Solar-powered drip irrigation can be installed in most gardens using a small solar system, readily available irrigation materials, and minimal tools. If you already have a home solar system, it can be tapped into without installing a dedicated system. And the installation of an average drip irrigation system is well within the abilities of most DIY enthusiasts.
Drip irrigation (micro-irrigation) is a system that applies a small, controlled flow of water directly to a plant’s root zone. It is an extremely efficient way to irrigate plants of all types in most gardens and climatic zones. The main benefits of drip irrigation are minimal water loss, minimized fertilizer leaching, and reduced foliage wetting.
In a solar-powered drip irrigation system, all the powered components draw their energy from a modest, dedicated solar power system. This would typically consist of a single solar panel, a charge controller, and a battery depending on the specifics.
In most cases, the need for a solar power source would indicate a lack of a municipal water supply. So a solar-powered pump would move water through a filter and a pressure reducer into the drip system. The drip system would consist of main feeder lines, sub-feed lines (if necessary), and drip tubes.
The main lines feed the water to strategic central points. The sub-feed lines then divert to the individual beds. Dripper irrigation tubing then feeds the water to individual plant positions. Drip irrigation tubing is terminated with various fittings that slowly deliver water to the plants’ root area.
Drip tube fittings are calibrated to deliver fairly precise amounts of water to the plant avoiding over or under-watering. The watering time is usually controlled by a timer, so exact irrigation control is possible.
How Does Drip Irrigation Work, and What Are Its Benefits?
Drip, or micro-irrigation, uses a slow trickle of water to wet the soil in a focused area around the plant. The process involves pumping water through irrigation tubing that terminates at the base of individual plants. Unlike sprinkler irrigation, drip irrigation systems deliver moisture that targets the plants’ roots specifically. This prevents water runoff and almost eliminates evaporation losses even in sweltering weather.
A slower flow will penetrate deeper into the soil in a narrow area for any given water volume. A faster flow penetrates less but covers a wider area. This allows for fine control of water available for plants with differing root structures, as illustrated below.
Additional benefits are the absence of water on the plant foliage common with misting or spray irrigation. This, in turn, reduces the scorching of some plant leaves and the possibility of fungal growth.
And because the area immediately adjacent to the plant receives no water, weed growth is discouraged. This reduces competition pressure and encourages growth and health in the targeted plant.
Liquid fertilizers can be injected directly into the irrigation tubing, meaning less fertilizer is used in a more precise dispersion. Dripper irrigation also prevents excess fertilizer from leaching into groundwater sources. And sloping areas are also easier to irrigate due to the absence of flooding runoff.
In short, drip irrigation is highly effective, efficient and cuts back significantly on cost and labor. When compared to sprinkler irrigation, there are some drawbacks to dripper irrigation, though.
Here’s a list of the pros and cons of dripper irrigation systems.
- Highly efficient. Water savings of up to 90%.
- Highly effective. Unmatched water and nutrient dispersion.
- Weed control.
- Garden slope flexibility.
- Elimination of foliar scorching and fungal contamination.
- Reduced fertilizer use and the associated risk of groundwater contamination.
- Requires rigorous filtering. Waterborne contaminants, silt, and high iron content can quickly clog the small emitters and tubing.
- Rodent, insect, and traffic damage. Because the majority of the piping is surface mounted, it is susceptible to this type of damage.
- Relatively high maintenance requirements. See all of the above.
Building a Solar-Powered Drip Irrigation System
Installing a DIY solar power drip irrigation system may seem daunting because of all the detail and moving parts. In reality, though, it’s not that complex at all.
To demonstrate, we’ll walk you through a step-by-step guide to planning and installing a mid-sized vegetable garden drip irrigation system. The drip irrigation system is solar-powered and located in a climate zone where drip systems excel.
An Important Note
This solar drip irrigation model is going to be complex. Far more complex, in fact, than it would typically need to be. There’s an excellent reason for this philosophy, though.
We will try to include as many different solar power and drip irrigation techniques, equipment, and parts. We will also include garden techniques and plant types that may not be obvious choices for many.
While we could have used a straightforward model, although complex, this example should serve two purposes. Firstly, it’ll be a good example of the wealth of potential solar power and drip irrigation systems. And secondly, it’ll hopefully be a valuable guide on how to implement solar drip irrigation anywhere.
So, bear with us and remember this. Nothing in our little drip irrigation garden is stuck in stone. All equipment, dimensions, parts, and techniques we have included are strictly examples only.
How We Have Planned Our Garden: The Geography
We have chosen to locate our garden in a semi-arid to an arid climate. Typical examples would be Arizona, Utah, New Mexico, and Nevada, to name a few.
Ideally, the target area would experience temperatures from extreme lows of 36°F and extreme highs of 95°F. In addition, the area would experience a rainfall average ranging from lows of 0.1 inches to 3 inches.
Although they may seem extreme, the reasoning behind this choice of a geographic location and conditions is simple. These are some of the most challenging irrigation and gardening conditions possible. They are also the exact conditions where solar power and dripper irrigation come into their own.
Water and Power Sources
We have worked on a voluntary off-grid design philosophy for the model’s water and power requirements. To clarify, while there is access to municipal power and water, we choose to use solar power and well water.
The reasoning behind this choice is the opportunity to demonstrate how low-cost, renewable resources can suffice in this environment. In addition, the model will show how municipal grid supplies can be tapped into the system to serve as backups.
The Garden Size
We’ve chosen a garden plot of 40′ x 25′ for a total area of 1,000 ft². It is typical of the size of the garden that would grace the properties of smallholdings and off-grid homesteads. In truth, the beauty of drip irrigation is the way garden dimensions can be scaled up or down with ease.
This is a basic layout diagram of the garden showing the main features.
The Plant Selections
Our dripper irrigation model will be based exclusively on vegetable crop plants, herbs, and fruit trees rather than ornamental varieties.
The crops we’ve chosen are:
- Tomatoes (celebrity hybrid)
- Peppers (bell)
- Pole Beans
- Vine Cucumbers
- Summer squash (zucchini)
- Head lettuce (iceberg)
- Bonanza Dwarf Peach
- BlackJack Fig
The beds we have chosen are representative of this sort of garden and are:
- In-ground beds
- Raised beds
- Supported raised beds
- Containerized beds
The Drip System Specifications
To work out the specifications for this system, we’ll start at the drip point end and work our way back. This is essential because the number of drip points will dictate the water delivery requirements of the system. This, in turn, will define the pump size and ultimately the solar system specifics. So the main logical progression points in planning the system are as follows:
- Define your garden layout. This will include the number and types of beds and what you intend to plant in each. Each plant type has specific spacing and watering requirements, so knowing your layout is integral to sizing the system.
- Plan your pipe layout. Draw a diagram for the layout of your main, sub-main, and drip hoses using the garden layout as a guide. Try to avoid crossing access paths with any of the hoses. This will allow you to calculate the total length of each hose size you’ll need. Always add a safety margin of 20 percent to each length.
- Calculate drip point requirements. Using your garden layout as a guide, work out the size and quantity of drip points you’ll need.
- Calculate the supplemental fitting requirements. The pipe layout will allow you to work out how many other fittings you’ll need. These include in-line connectors, T pieces, elbow fittings, barb connectors, and goof plugs.
- Calculate the pump size. Solar-powered pumps are sized according to the gallon per hour (GPH) requirement you worked out in your drip point calculations.
- Design your drip and well pump solar power systems. Knowing which pump you’ll use and how long it’ll work every day is the first step in defining your solar system. In addition, ancillary equipment like lighting and AC outlets you choose to include in the layout will add to the system requirements.
There are several additional planning steps that slot in between the main points. These include designing your water storage and feed setup and planning your backup power and water systems. These will be covered in more detail later.
Now, let’s consider each of these main points in detail according to our overall model specifications.
The Garden Layout Overview
The Plant Layout
Our garden model consists of 9 separate “zones.” The bed types are outlined above, with several beds lying fallow. The plant distribution is illustrated below.
The types and bed layouts of the different vegetables in this model have been chosen for the following reasons.
- They are typical of the crops grown by small-scale farmers or homestead owners for their own use.
- The bed layouts demonstrate different types of typical dripper irrigation methods.
- The layout is a good example of calculating material quantities, total drip rates, and pump size. This, in turn, allows for the planning of the solar system and water supply requirements.
The Piping Layout
The garden’s piping layout has been designed according to the following specifications.
- Minimum use of piping.
- Ease of access for maintenance.
- No piping crossing traffic ways.
- Isolation valves allow for zone control during irrigation runs.
The piping layout and bed types are illustrated below.
The pipe quantity calculation for this garden is as follows. Note: Each pipe type has added a 20% safety margin, and the figures are approximate estimations.
- ¾ inch mainline – 140′
- ½ inch sub-mainline – 130′
- The ¼ inch plain drip line – 40.’
- ¼ inch integrated PC dual dripper line (6″ dripper spacing) – 6′
- ¼ inch integrated PC dual dripper line (12″ dripper spacing) – 18′
- The ¼ inch integrated PC single dripper line (12″ dripper spacing) – 18′
- ½ inch integrated single PC dripper line (36″ dripper spacing) – 30′
The smallest rolls of drip tubing are usually 50′ long, so the purchased totals would usually be far larger. It may be possible to find shorter rolls or have them cut to your specification, but this would be the exception rather than the rule. Considering the life span of this type of project, having excess material is not a bad thing at all, though.
Here is a condensed list of the piping requirements with supplier links.
- ¾ inch drip irrigation mainline.
- ½ inch drip irrigation sub-mainline.
- ¼ inch drip irrigation microtubing.
- ¼ inch integrated PC dual dripper line (6″ dripper spacing)
- ¼ inch integrated PC dual dripper line (12″ dripper spacing)
- ¼ inch integrated PC single dripper line (12″ dripper spacing)
- ½ inch integrated single PC dripper line (36″ dripper spacing)
The Drip Point Layout
Drip Point Totals
The total number of drip points for the garden model is as follows.
- Conventional drip points – 25
- ¼” Pressure compensated dual drip points – 12 (6″ spacing)
- ¼” Pressure compensated dual drip points – 26 (12″ spacing)
- ¼” Pressure compensated single drip points – 16 (12″ spacing)
- ½ ” Pressure compensated single drip points – 8 (36″ spacing)
This makes for 87 drip irrigation emitters in total. The plants chosen for the model have differing drip-rate requirements that range from 0.5 to 1 gallon per hour (GPH). To simplify the layout, an average drip rate of 1 GPH will be used throughout. The isolation valves and the pump timer can then be used to fine-tune the watering. More on that later.
Based on these factors, the total water requirement of the system would be 87 x 1 or 87 GPH. With a 20% safety margin to that figure would be around 105 GPH.
This is a fairly long list and takes some careful thought to calculate correctly. Even so, the fittings in question never go to waste. They will constantly be replaced or used in route changes or extensions, so buying in bulk is not bad. Here’s a list of the fittings you’d need to build our drip irrigation model.
- ¾ inch barbed 90º elbow fittings.
- ¾ to ½ inch T connectors
- ¼ inch barbed straight connectors
- 1 GPH pressure compensated drip emitters
- 0.5 GPH pressure compensated drip emitters (optional)
- 2 GHP pressure compensated drip emitters (optional)
- ¼ inch adjustable drip emitter/spray heads (optional)
- ¼ inch goof plugs
- ½ inch Fig 8 pipe stop ends
- ½ inch end stop fittings (optional)
- ¾ inch end stop fittings
- ¼ inch tube stakes
- ½ inch tube stakes
- 1-inch pipe retainer staples
- ½” x 8″ garden stakes
Choosing the Drip Irrigation Pump
The pump chosen for this, or any other, system should at least handle the maximum circuit GPH rating.
According to the specifics of our garden, we have chosen a 12 volt, 3 gallons per minute (GPM) transfer pump. This will deliver 180 gallons per hour which are more than we need. However, the pump includes a pressure regulation switch that can keep the delivery pressure at the 30 PSI our system requires.
Designing the Drip Irrigation Solar System
Our drip irrigation system uses a fairly simple solar system as its primary power source. There is a supplemental 120 volt AC main feed used to power the system if necessary.
For the sake of simplicity and cost efficiency, the solar setup doesn’t include an inverter. It consists of a solar panel, a charge controller, and a battery.
The garden AC outlets draw from the mains power grid. Ac outlets are a handy addition if one needs to use power tools or equipment in and around the garden.
The Core Solar System
The solar system chosen for the project is an 0ff-the-shelf Renogy 100-watt starter kit. The kit consists of a 100-watt solar panel with extension cables, a 30 amp PWM charge controller, and mounting hardware.
This solar kit is pretty impressive and packs more than enough punch to power the system for a very reasonable price. In the PWM vs. MPPT stakes, the Renogy Wanderer doesn’t give much away, largely due to the environment and system size.
PWM charge controllers do well in hot, sunny environments, and our system is modest, so a PWM controller isn’t a liability. The 30 watt Wanderer has great features, including battery temperature compensation, and will handle up to 4oo watts of solar panel output. This means if you needed to, you could add another solar panel or even put together a multi solar panel array.
The only downside of this controller is the lack of an LCD status display. In practical terms, this is not that much of a pain. However, it is nice to be able to track the performance of the system at a glance.
We will be running a 12-volt pump with a starting amperage of around 7 amps and draws just over 4 amps during operation. On a typical day, the pump would run for 30 to 45 minutes in the morning and the same in the late afternoon. All things considered, we could use a battery of around a 12 Ah rating and AGM, SLA, or LiPo construction.
We’ve opted for a larger LiFePo battery of a 24 Ah rating. There are, of course, far cheaper batteries on the market, but few can match the long-term benefits of lithium batteries. This battery would also allow us to expand our layout quite a bit before adding extra batteries.
The solar system and battery in overview:
- Renogy 100 watts, 12-volt monocrystalline starter kit complete with solar panel.
- DC House 12 -volt, 24Ah deep cycle battery with a built-in battery management system.
Supplemental Electrical Equipment
The installation as a whole is going to require several non-solar-related components. The function and layout will be dealt with in detail in the circuit description a little later. These components are:
- 2 x double pole 500 volts DC max, 16 amp max circuit breakers – DIN rail mount*
- 1 x double pole 400 volts AC max, 40 amp max circuit breaker – DIN rail mount*
- 120 volt AC to 12 volt DC switching power supply
- 35 mm DIN rail
- 14 AWG parallel 2 core panel wire – 20 ft
- 8 AWG parallel 2 core panel wire – 20 ft
- 6 way DC blade fuse box
- Pre-insulated spade and ring terminal selections
- 5 terminal negative bus bar
- Brady circuit breaker lockouts
- Programmable pump timer
* NOTE: When buying circuit breakers, ensure they are equipped with lockout holes as indicated below. This is essential to interlock the solar and backup systems. This will be covered later in this article.
Putting the Solar Panels and Components Together
The solar component of the irrigation setup is fairly straightforward. The circuit diagram below illustrates only the solar elements and pump system.
The Solar System Specifics
The solar panel outputs are fed directly into the charge controller (A). The controller charges the battery (B). A set of leads are connected from the battery to a 2 pole DC circuit breaker (C).
The outputs from the circuit breaker are connected to the positive DC fuse box and the negative bus bar (D). These two components serve as the distribution point for all the 12 volt DC requirements of the system.
Positive and negative leads are connected to the pump timer (E) in the actual irrigation system. The irrigation controller’s timer has an internal switch that starts the irrigation pump at pre-programmed intervals.
The last component of the solar part of the circuit is a manual override (F). This is a simple toggle switch that lets you start the pump without messing with the timer settings. It’s a great feature for testing the solar-powered water pump or flushing the system.
The Need for a 12-Volt Backup System
The geographic location of our garden model is ideal in terms of solar efficiency. Even so, you will certainly need a backup power source occasionally.
A backup 12-volt system is essential to ensure your crops are watered on time in cases such as these. That backup comes courtesy of a 120 volt AC to 12 volt DC switching power supply unit (PSU) in this model. The PSU is supplied by the AC grid power source and connects directly to the DC system via its own circuit breaker. And that point is of vital importance.
Backup Power and Interlocking
In any electrical supply grid that features backup power, it is absolutely critical that the primary and backup supplies can’t be run together. Even if the primary supply is isolated, starting your backup with the primary still connected can be disastrous.
For this reason, it is essential to be able to isolate both primary and backup systems. And equally important to ensure that they are never activated together. And this is why we have included circuit breakers (CBs) for both primary and backup systems. In addition, our note to buy CBs that have lockout facilities will now become clear.
Activating the AC Main Backup
At this point, we can look at the complete circuit diagram with the AC mains feed and 12-volt backup system included.
The AC mains feed comes into the system through a dedicated AC circuit breaker (E). Ideally, this CB will feed all the AC outlets in the garden layout. A couple of those would be located in the solar hut or shed and must be switched outlets as indicated.
The backup switching power supply unit (A) would be fed one of the switched outlets. The PSU’s 12-volt output is connected to a dedicated 2 pole circuit breaker (B). The CB output is connected directly to the DC fuse box and negative busbar (C). So, essentially you have two separate 12 volt DC feeds to the fuse box and bus bar. And that’s where things get interesting.
Switching Between Primary and Backup 12-Volt Supplies
As mentioned previously, you cannot have two independent power supply sources connected. So, in a solar system failure, you must follow a specific procedure when switching to your backup supply. And now the importance of that little red Brady CB lockout doodad (D) becomes clear. Here is the procedure step-by-step.
- Switch off the CB for the solar PV panels.
- Remove the lockout device from the backup CB.
- Lock the solar CB with the lockout device.
- Switch on the backup CB.
- Switch on the PSU outlet and make sure it’s running.
- Use the manual override to test the pump.
When you want to switch back to solar power, reverse the procedure. NB. Make sure you switch the backup CB off and lock it out before switching the solar CB back on again.
Irrigation Water Supply System
A reliable and predictable water source is the heart of drip irrigation systems. Let’s look at how we have designed our water supply and storage.
Primary Water Source
Our solar drip irrigation model uses a 330-gallon IBC tote tank to supply water to the garden. If we run two 30 minute watering cycles each day, we would consume around 180 gallons in 24 hours. That’s a little more than half a tank each day.
Our model uses well water to supplement the holding tank water supply. An in-tank float switch starts the well water pump when the tank level falls below a set point. In this case, it would be set to activate when the tank reached around 150 gallons. When the tank is full, the float switch will turn the well water pump off.
The average 1 HP deep well will deliver more than 1,000 gallons per hour from 100 feet or more. So, your well water pump should run for less than 15 minutes per day to keep your holding tank full.
Water storage tanks are normally the most expensive components in self-contained drip irrigation systems. For example, a new tank of the type we chose is close to $700. You could add more tanks if you need additional holding capacity, but that would obviously mean significant financial outlays.
Supplemental or Backup Water Source
As our garden has access to a municipal water supply, any failures of the well water source could easily be addressed. The municipal supply taps into the holding tank supply circuit with a manual switch-over valve.
Irrigation Pump System
Our solar-powered water pump is situated in the solar system shed. This keeps it out of the elements and eliminates lengthy exposed cable runs. The pumps used for solar-powered drip irrigation setups are very similar to solar fountain pumps.
The pump setup is illustrated below.
The incoming water feed from the holding tank first passes through the pump’s supplied inline filter (A).
The delivery side of the solar irrigation pump circuit includes several critical components. The first of these is a backflow protector (B). When the pump is switched off, this device stops water from flowing back into the pump from the garden circuit.
The second component is a pressure reducer (C) rated at 30 PSI. Our pump does have an adjustable pressure regulator, but the additional reducer offers good redundancy. A separate pressure gauge (D) would also be a handy but optional addition.
The second optional redundancy measure is a delivery water filter (E). Although it’s strictly not necessary, it does add a level of contamination protection. Drip irrigation emitters are notoriously easy to clog, so extra filtration is never a bad thing.
Irrigation Water Supply and Storage System
As we’ve described earlier, our garden model’s water is pumped from a well and stored in a holding tank. Ideally, the well water pump and related systems would be solar-powered. However, considering the shallow run times for the pump, the expense of a solar system may not be justified. On the other hand, if the well supplied water to the rest of the home, it may be a sound investment.
This is what the municipal supply layout looks like.
Water from the well (A) passes through a sediment filter (B) and is pumped into the tank (G) by a jet pump (C). A three-way valve (E) is located in the tank feed line that controls which water source is used. If a problem arises with the well water or the pump, the municipal water supply (D) can be engaged *.
The pump is activated by a pump starter contactor (F). The starter is, in turn, switched on by the input from a float level switch (H) in the tank. This system does a good job of regulating the tank level IF the well water is the source.
*IMPORTANT NOTE: If you engage the municipal supply, you’ll have to monitor the tank level physically. With the system as it stands, the float switch cut-out ONLY regulates the well water pump.
The last component in our irrigation system’s supply and storage is the garden water feed outlet (I). Fortunately, because of the tank’s proximity and size, you won’t need to raise it to create head pressure. When full, there are around 3,000 lbs of water in the tank. Even when half full, the weight of the water will supply enough pressure to keep the system functioning perfectly.
Laying Out the Drip Irrigation Piping
We will now detail how to install all of the drip irrigation piping. We’ll systematically approach this by breaking the system into mainline, sub-mainline, and zone-by-zone drip line sections.
Installing the ¾ ” Mainlines
As illustrated below, the garden mainline system runs around the area’s perimeter in an approximate U shape. At this point, our garden is already roofed and fenced, so we have a clear perimeter demarcation.
Note: When installing barbed fittings on ¾ and ½” tubing, it isn’t necessary to use hose clamps. This is largely due to the low operating pressure of drip systems. Many installers believe in using them as an added fail-safe, so we have included them in the mainline section. Additional clamps are not required at all on ¼” pipe runs.
The first step is to mount a piece of ¾ ” hose onto the compression fitting on the pump delivery (1). Now, push a ¾ ” elbow fitting into the pump hose and secure it with a hose clamp as illustrated. Now you can start laying out the perimeter tubing runs.
The tube roll will have developed fairly stubborn coil memory. So laying the runs out straight can be tricky and is usually a two-person operation. One of the easiest ways to get your assistant to hold the free end of the hose at point (2). Now you can walk back to the far corner at point (3), allowing coils to slip off the roll as you go. Remember to take a handful of hose staples with you.
When you get to the corner, lay the roll on the ground and pull the hose straight. It’s unlikely to straighten out completely, but that’s ok. Just make sure you don’t kink the hose. Now, leaving some slack, cut the hose and secure it with a hose staple or two. Your assistant can similarly secure the other end.
Rinse and Repeat
Repeat the process with the other two sides of the circuit and sit back and let the sun do its magic. After a while, the hose will soften up and become more pliable and cooperative. At this point, you can start installing the elbows and cutting the tube runs to their final lengths.
Start with the free end of the pump hose elbow fitting and secure the first run with a hose clamp. You Now work your way down the run, straightening it out and securing it with staples every 6 feet or so.
Note: When using hose staples, don’t kink or obstruct the hose. Just push them into the soil until they secure the hose with enough room to move it from side to side.
You can cut off any slack and install another elbow fitting when the first run is straight and secured. At that point, you can attach the free end of the short-run hose to the elbow fitting as well. Place a staple close to the fitting on both hoses and work on straightening and securing the short run.
Once done, the last run can be straightened and secured. The last step is to push the end cap into the open end of the last run and secure it with a hose clamp.
Important note: When laying out any drip irrigation hoses, it is essential to be very careful not to allow any dirt to get into the hose. When doing layouts like this, use figure-of-8 hose closures to keep open ends from gathering dirt. Or you can run the hose end through a staple twice and hammer it down good and tight. In any case, it’s good practice to flush main and sub-main lines before installing the drip tubes and emitters.
Installing the ½ “ Sub-Mainlines
It’s easier to lay out sub-mainlines because they are seldom longer than 8 feet. However, there are more components involved making the installation as a whole more complex. Again, our zones are already clearly marked out, and the positions of the lines are depicted below.
To tie the ½” tubing into the larger mainline, I have chosen an interesting and very functional fitting. These combination ¾ x ¾ x ½” T fittings with integrated isolation valves feature compression connections. They reduce the number of separate components involved from between 5 and 7 to only one.
We are also using compression-fitting endcaps that are equally easy to fit. They also have removable caps, so flushing the lines is quick and simple.
To install the sub-mainlines, start at a position (1) and measure and cut the first sub-mainline using the mainline layout methods. Now you can trim the mainline and install the T fitting. The trimming process is illustrated below.
Use the fitting to measure how much of the mainline you need to remove. Use your tube cutter to cut out the excess tubing remembering it’s better to cut out too little than too much. Now you can insert the fitting into the mainline and install the sub-main at the same time.
The following video is a good description of how to install drip irrigation compression fittings. Video
Once the valve T fitting is in place, you can cap the sub-mainline with the compression endcap. The process will be identical to the video instruction. Now that the first sub-mainline is installed repeat the process for each garden zone or area.
Installing the Drip Irrigation Lines
Each bed in our garden is watered using a variety of different drip irrigation lines and emitters. For the most part, we have used ¼” drip lines. The only exceptions are zones 2 and 3 (pumpkins and squash) that use ½” pressure compensated (PC) emitter tubing.
Before we dive in, let’s look at the different drip irrigation tubing types we have used.
We’ll detail the dripline installation according to zones with common line types. For example, zones 1, 2, 3 & 6 all use integrated PC dripper emitters and will be detailed together.
Zones 1, 2, 3 & 6 – Integrated Emitter Drip Irrigation Lines
Pressure compensated (PC) integrated emitter drip irrigation lines have internal emitters built into them at regular intervals. Holes punched through the outer wall of the tubing allow a controlled flow of water to reach the plants. They’re either single emitters with holes on one side of the tube or dual emitters with two holes opposite each other.
The PC designation means the delivery pressure remains the same throughout the entire length of the tube. Of course, you have to stick to the manufacturer’s designated maximum run lengths for this to work.
Working With Integrated Emitter Drip Tubes
One issue many users encounter with these tubes is water wastage between the mainline and the first plant positions. As the tubes have emitters at regular intervals, there may be several locations with no plants. Here is a handy way of getting around that problem.
Cut the integrated emitter tubing to size according to the plant distribution in the bed. Then use a ¼” straight barbed connector to join a piece of regular ¼” drip tubing to the PC tube. Now tie the regular drip tube into the mainline with another barbed connector.
Now that’s out of the way, let’s get into drip lining our first zones.
Zone One and Six
Zone one and six are very similar layouts. Two are planted with 8 head lettuce plants (Iceberg); the third has been left fallow. Zone one consists of three 6′ x 2.5′ raised beds. The integrated emitter hose construction has been described above and consists of one 12″ spacing run comprising 4 emitters per bed.
The plant row spacing allows the dual emitter drip line to do a good job of watering both rows simultaneously. The layout is illustrated below.
When the bed’s integral emitter hose is cut to size, splice it into the blank water saver drip hose. Then you can punch a hole in the ½” mainline and connect the drip line to the sub-mainline. Repeat the process for the second bed and insert goof plugs into the ends of both drip irrigation lines.
Zone six is very similar to zone one in that it has two beds fed by integrated emitter drip tubes. However, in this case, the drip tubes are single rather than dual emitters. Outside of that, the installation process will be identical to zone 1.
Zones Two and Three
These zones are large in-ground beds for ground vine plants, namely pumpkin and summer squash (zucchini). There are 4 plants per bed, and they are irrigated by ½” emitter tubing at 1 GPH and 36″ spacing.
We will be using ½” x 3 barbed T fittings to tie the drip line into the mainline without hose clamps. For these beds, we’ll use figure-of-8 hose end caps. This is what the layout will look like.
To install the T fittings, cut out the excess sections as you did with the mainline. You can then measure and cut off two sections of ½” emitter tube.
Push the sub-mainline and emitter tubing over the fittings until all the barbs are covered. Now you can trim off any excess emitter tube and install the end caps.
To use the figure of 8 end caps, pass the end of the emitter tube through the first opening of the end cap. Then double it over and pass it through the second opening.
Now snug the end cap down towards the fold as far as it will go. This tightly kinks the hose shut and prevents leaks while being easy to remove to flush the line.
Repeat the process for the remaining bed to complete zones 2 & 3.
Zones Four and Five
Zones 4 and 5 each have a single dwarf fruit tree in the zone. Large bushy plants and trees benefit from a drip irrigation technique known as a drip ring.
Drip rings are drip tubing formed into a circle to distribute water around larger bushy plants or trees evenly. But why are they so effective?
An Explanation of Plant Root Zones
As part of the evolutionary process, most plants’ root systems develop according to the “canopy” size of the plant. In other words, the farthest a plant’s root system will develop is the extent of its canopy or drip zone.
This ensures that all the plant’s canopy catches water drips into the root zone when it rains. At the same time, the plant’s central or tap roots develop deeper, harvesting water from longer-lasting deep water saturation zones. Installing drip rings to irrigate trees of larger bushy plants, you can ensure that the entire root system benefits.
This is illustrated below.
Drip rings are drip tubing formed into a circle to distribute water around larger bushy plants or trees evenly. Drippers are then installed in the ring to water the appropriate area.
For large trees, a ½” drip ring or drip ring combination works well. This type of drip ring allows you to water the main taproots and the drip-zone roots simultaneously.
The basic concept is illustrated here for small and large trees or bushes.
For smaller bushy plants such as tomatoes, beans, and trellised vine plants, you could opt for a ¼” arrangement as detailed here.
Both tree varieties in zones 4 & 5 grow between 6 and 10 feet tall with the same canopy width. Considering the canopy size and 1 to 1.5 GPH watering requirements of both, a ¼” drip ring system is ideal. A detailed description of both types of ring irrigation layouts is illustrated here.
Zones Seven and Nine
Zones 7 and 9 are the most “conventional” drip irrigation layouts of the garden. They consist of blank ½” drip tube runs and conventional drip emitter fittings. Zone 7 features 2 beds with three plant positions each and one 5 position bed. Zone nine is a high tunnel greenhouse with 6 tomato plants in 3 rows with two plants each. The drip rate for all the plants is the usual 1 GPH.
Zone 7 requires you to fit ½” compression T fittings into the sub-mainline irrigation system at the edge of each bed. Then, an appropriate length of ½” blank drip tube is run down the length of the bed as indicated. Once it’s cut to size, connected it to the T fitting and used staples to secure it.
Here’s the zone 7 drip tube layout in graphic format.
Before we discuss the individual drip irrigation lines, here’s a quick tip. Some folks simply install a drip emitter straight into the ½” tube or use an extension as illustrated in (A) below. Although this way of doing it is essentially correct, it does create a risk of dirt clogging the emitter. A better method of installing individual emitters is detailed in (B).
To install the drip lines for zone 7, use the hole punch to make holes adjacent to the plant positions. You can then use either of the methods detailed above to tie a drip line into the sub-mainline. Repeat the process for all the plant positions.
Zone 9 is a high tunnel greenhouse for tomatoes. This zone demonstrates that a drip irrigation system in PVC tunnels or greenhouses is the same as outside bed layouts. In this case, the set-up is identical to zone 7.
The layout is illustrated here.
The last of our garden zones is zone 8, consisting of 2 supported raised beds and 4 plant containers. Containers and raised beds feature the same basic dripper irrigation principles as any other but need some tweaking.
The main difference between them and ground-level beds is the need to raise the sub-mainline. This takes some work and a bunch of components but isn’t hard to do. Let’s describe the two types of irrigation systems one at a time.
Supported Raised Beds
Supported raised beds are essentially boxes filled with soil. They offer gardeners many advantages, including reduced soil compaction, better drainage, and they warm up earlier in spring. They’re also great options for folks with reduced mobility.
Getting your drip watering system into a supported raised bed involves adding a T fitting into the sub-mainline with a riser tube. This arrangement is typically located at one corner of the box. An elbow joint is added to the riser tube, which directs the sub-mainline to the rest of the box.
Once the sub-mainline has been raised to soil level, convention drip watering system techniques can be used.
Here is a great video on drip irrigating raised gardens. Video
To expand on the concept, here’s an illustration of how it comes together.
Raising the Sub-Mainline
In our raise box beds, our sub-mainline irrigation system is a short way from the box. So we attached a short link tube (B) to the T fitting to bring the feed to the corner of the bed box. An elbow fitting (D) is attached to the link tube with its free end facing towards the top of the box.
Our riser tube is attached to the free end of the elbow and trimmed flush with the top surface of the box. Then we attached the second elbow fitting to the open end of the riser tube. The free end of the fitting is now facing along the short side of the bed.
Now we attached a short run of ½” tube to the free end of the elbow fitting. The final piece of ½” tubing (C) runs along the bed’s short end and is terminated with an end cap (I).
Installing the Drip Line
The rest of the drip line installation (F, G & H) is simple. It is essentially identical to the dual opposed drip line in zone 1 in all aspects.
Containerized herb and vegetable gardening are prevalent, and drip irrigation of containers deserves mention here. We have four large oblong containers in zone 8 with two herb plants per container.
The same basic raised box bed principles apply here, with us having to raise the sub-mainline to the soil level. However, in this case, we don’t need link tubes, with risers exiting directly from the T fittings (A).
We also include an elbow fitting at the top of each riser (C). But, unlike the box beds, they face along the length of each container group. A ½” distribution tube runs from the elbow across the middle of each group of two containers (D). This distribution tube is secured with 8″ x 12″ garden stakes (G) and terminated with end caps (E).
Once the distribution tube is installed and capped, the drip point installation (F) is the same as zone 9.
This is the overview of the zone 8 layouts.
This is a pretty big and complex container drip irrigation setup. That’s not to say all pots and containers need this scale of drip irrigation. The illustration below shows how simple it is to use drip irrigation for even the smallest pots and containers.
Testing All the Solar Power Drip Irrigation Systems
At this point, the solar system, water supply, and garden drip irrigation system layout are complete, and the entire system can be tested.
Testing the Solar System
Before you test the drip irrigation system, ensure you have at least a ¼ tank of water in your holding tank. Also, check that the water supply valves are set to feed on the tank, and the sub-mainline valves are open. In addition, check that you have around 14 volts in the battery.
If your pump timer has an override function, you can use that to start the pump. If not, set the timer for a minute in advance with a 45 minute run time and wait for it to start the pump. When the pump starts, check that the pressure gauge is registering positive pressure and the PSI reading. It should be around 32 PSI.
If the solar system is running correctly, engage the backup power. Remember to follow the switch-over procedure listed earlier. With the municipal power engaged, the pump should run normally. Now reverse the procedure and continue testing on solar power.
Suppose the pressure is correct check all the pump connections for leaks. If you’re happy with the pump connections, start with the first mainline connection and work your way through the entire setup.
Testing the Drip Irrigation Lines
You will be checking that none of your connections leak and that all the drip emitters are feeding water. This is likely to take a long time and shouldn’t be rushed. Pay special attention to the goof plugs and end caps that terminate drip lines. As you progress, write up a snag list of any problems along the way – there are sure to be at least some.
If all your drip irrigation system connections seem sound and the drip lines feed water, you can stop the pump.
Drip Flow Rate Testing
If checking the general operation of the system took a long time, then this step is next-level. This is a step that is the best approach over a period of time. And only after you are confident that all the rest of the parts of the system are working correctly.
To calculate a dripper flow rate, you can use this basic formula. One gallon is equal to 128 fluid ounces. A 1 GPH dripper should deliver around 2 fluid ounces (± 60 ml) or a ¼ cup of water per minute. You can use a small measuring cup or jug to do random tests of drippers. This will show if the watering system flow rates are approximately correct.
And we use the term approximately purposely. This is not an exact science, and you’ll seldom ever get clinically accurate drip rates. Most reputable parts suppliers for drip irrigation systems take QC seriously, though, so the results should be pretty close.
Running the System Going Forward
When you check all the parts of your drip irrigation system for snags, it can be put to work.
This is another one of those inexact science things. Generally, watering in the early morning and late afternoon is good practice. A 30 to 45-minute water run twice a day should deliver enough water to ensure all of your plants’ good health and growth. But again, that’s something you will have to monitor and adjust according to the realities on the ground.
The zone isolation valves allow you to exclude certain areas of the garden as the need arises. They also allow for fairly fine control of the water flow to any given zone. So, all-in-all, this drip irrigation system is functional and relatively easy to manage.
On that note, if your budget allows for expansion later, this system can be almost completely automated. A sophisticated irrigation controller and powered solenoid valves can take almost all the leg work of irrigating the garden.
The same goes for the municipal water supply backup. With some extra wiring and a solenoid valve in the municipal water line, you won’t have to monitor the tank level.
Although they generally don’t come cheap, fertilizer injectors are a great way to automate fertilizer addition to drip irrigation systems. Here is an example of a fertilizer injector install in a drip watering system. This injector uses water flow to pick up and mix the fertilizer, requiring no external power.
This solar drip irrigation system guide has been lengthy. And yet, it hardly touches on the huge potential benefits that both disciplines can offer. Hopefully, you will have learned some valuable lessons on implementing solar drip irrigation in your environment.
Both solar power and drip irrigation are at the forefront of their respective areas of sustainable and environmentally friendly living. And both are well deserving of serious consideration when planning any home crop cultivation projects.
If you have any questions or comments regarding this guide, please feel free to post them in the comments section below.
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