Drip Irrigation Basics

Many farmers and gardeners have discovered that drip irrigation produces healthier plants, better yields, and it is a great time saver. The use of drip irrigation has decreased the incidence of plant disease that can occur with the use of overhead sprinkler irrigation. Plus, many water-soluble fertilizers can be applied through the drip system, thereby keeping nutrients near the root zone and allowing the plants to get the most value from each fertilizer application.

Most of the drip components were originally derived from Israeli engineers who were the pioneers in this field. Since then many systems have been devised in the United States, being field tested in California, Florida and Hawaii.

The advantage of a drip system is that you water the plants you want to water, keeping weed growth out of your plantings. And you don’t have to worry about whether you have stood there long enough with the hose (most of us never do!) or whether there will be enough rain to keep the plants going.

If you have ever put something together with Tinker-Toys, you have the basic ability to put together a drip system. It is that simple! Just get the components you need and assemble the system—most home garden systems can be assembled in one afternoon.

How CLEAN is your water?

The main question you need to answer concerns the quality of your water. While there are things which can be done to mitigate the effects of bad water, the dirtier the water, the more care must be taken when choosing the components needed to achieve the satisfaction and low maintainence with your drip system.

From most easily clogged to hardest to clog:

1. drip tape such as T-Tape & Chapin Tape

2. small orifice emitters such as 1/2 gph emitters

3. larger orifice emitters such as 1 and 2 gph emitters

4. minisprayers & sprinklers over 3 gph

5. in-line emitters such as Netafim & Dripperline

Within each classification, there are differences in the performance of various products (advantages and disadvantages) so don’t take this as an ironclad rule of thumb.

The worst water is from ponds or lakes that have algae and other suspended particulates. Just above that is water containing iron slime bacteria (these will not filter out, they only come out of solution when they hit the air). Equally bad is water that contains calcium or magnesium that will precipitate out when it hits air thus leaving deposits. Then comes water that has high levels of sand (many wells pump some sand). Believe it or not, even some municipal water systems have “crud” (a technical term) in their water, although most city water is pretty clean.

What Every System Needs

All drip systems should have a filter on them, regardless of water source. It is very cheap insurance so contaminants in the water clog the filter, not the emitters. Some people don’t like how often they have to clean their filter—if that is the case, get the next largest size so you won’t have to do it so often. Some systems require cleaning out the filter every time the system is run and some people only have to do it once a year (depends totally on your water quality).

Most drip systems should have a pressure regulator—especially if you are on city water or have a well set to run between 40 and 60 psi. If you are on a spring box or have a gravity fed tank with not much head above the drip system, you probably won’t need a pressure regulator. Most emitters and minisprinklers are designed to give the rated gallonage at 20 to 25 psi. Most soaker type tubing is designed to run at 10 to 15 psi.

Choosing Components

How do you choose which types of emitters, soaker type tubing or minisprinklers you want for your system? It is an individual choice and here are our recommendations on what most people have found to work well for them:

Emitters—Generally, people choose to use emitters when the plants are spaced somewhat far apart as is the case with perennial shrubs, fruit trees and vines and vegetables planted in hills. On flat ground you can use either the Jain Flag, Netafim button or 36” or 48” Dripperline emitters (can be ordered by request) for evenly spaced trees and vines. The Jain Flag emitters can be opened to be cleaned if necessary. The Netafim buttons cannot be opened but they very rarely clog. On hilly ground (greater than 20 ft. vertical change up or down a hill), one should definitely chose from the pressure compensating emitters(which can be either in-line or punched into hose) so that all of your plants get the same amount of water per irrigation. Only the Turbo SC emitters (of all the pressure compensating emitters) can be opened to be cleaned if necessary. All pressure compensating emitters are self-flushing.

Soaker type tubing and tape—these are ideal for watering intensively planted beds of vegetables or flowers, also berries, turf, and other areas where you want to evenly water an entire swath of plants.

Tape-type tubing(T-Tape or Chapin Tape) is primarily used by vegetable farmers, both large scale and small. Tape-type tubing must be used in straight runs— not around corners or bent (unless you use appropriate fittings) or the flow of water will be restricted.

Dripperline (Soaker Dripline) is often used in ornamental settings and can be gradually curved or bent without affecting its performance.

Tape-type tubing requires 10 psi operating pressure. Soaker Dripline should be used at 15 psi. Dripperline works best at 20 psi. Only Soaker Dripline, 12” Dripperline and 12” Pressure Compensating Dripperline are recommended where heavy iron (i.e. when water stains fixtures) or calcium is present in the water.

Mini-sprayers and Mini–sprinklers—These are used where people want to water a larger area. They can be utilized more like standard sprinklers in that there are many different patterns available for use, although the gallonage and radius involved is much less. This means more drip mini-sprinklers can be run on one line than would be possible with standard sprinklers. One thing you should be aware of is that the mini-sprayers and mini-sprinklers do not work well in heavy winds—due to the finer droplet size, they will not give you the desired coverage if operated when there is a lot of wind. You can compensate for this by running the system in the evening or early morning when wind is not usually a problem.

Drip Irrigation Systems Design

Start by making a sketch or scale drawing of the areas you want to drip. Note the location and size of plants to be irrigated, and whether they are native (and drought tolerant) or introduced (requiring more water), and the location of water sources. Note distances needed for tubing and what fittings will be needed to layout the system (tees, elbows, etc.). Based on the size and type of plant (see watering guide), determine how many and what type of emitters or sprayers will be required.

When designing your drip system make sure to plan for the future. When plants mature, they will require more water. This can be accomplished by watering longer but it is usually more satisfactory to add more emitters as plants grow at different rates. Also, new plants may be added to the landscape so leave about 25% more water capacity available for growth needs.

Garden valves and standard 3/4” sprinkler valves will almost always provide more than enough water for most home landscape/garden needs. To determine how much water the drip system will require simply add up the total number of emitters and their flow rates. (Example: 20- 1 gph emitters = 20 gph; 20-2 gph emitters = 40 gph; 20 + 40 = 60 gph total).

If in doubt about the capacity of a water source, simply time how long the valve takes to fill a measured container. (Example: If it takes 30 seconds to fill a five-gallon bucket, then the maximum flow available is 600 gallons per hour. The formula is to take the GPM x 60 to get GPH). Should the system require more water than is available, divide the system by using multiple valves or a hose Y connector and run one system at a time.

Because drip irrigation operates at low pressures, effects on pressure caused by changes in elevation should be considered if elevation varies over 20 vertical feet from water source. If elevation changes are a problem, use pressure compensating emitters.

When designing your drip irrigation system keep in mind questions like: Will it get in the way when cultivating, raking or weeding? Should the drip tubing be hidden from view? Is it out of the way of foot-traffic areas? In areas where gophers and other rodents are problems, no drip or spaghetti tubing should be buried or they will chew through it. Mulch can be used to cover tubing.

The following chart is useful in determining what size drip hose should be used as a main line (regardless of whether you are using emitters, soaker type tubing or minisprinklers).

First, design your system and add up the gallonage required as well as the length the main line tubing will have to run, then look at the chart to see what size drip hose you should use. Most home landscape/garden systems use 1/2” drip hose. Large systems should use 3/4” hose (or break the system into segments or use more than one faucet hook-up).

System Head or Manifold Assembly

At the beginning of your drip system, you should install a backflow prevention device or check valve to prevent back siphoning of irrigation water into drinking water systems. Most municipal building codes require the use of these devices. If you are on a well and plan to do fertilizer injection, you should definitely use one.

Depending on what type of filter and pressure regulator will be required for your system, PVC transition fittings may be needed to get from pipe thread to hose thread connections. Use teflon tape on all pipe thread joints (not pipe dope). Hose thread connections will seal with the washer included on them. Do not use a wrench to tighten plastic threads, hand-tighten only!

If you want to automate your drip system be sure to select a controller designed to water at least two hours per station. We feature a number of controllers which are appropriate for drip systems- many older controllers were designed strictly for use on standard sprinklers and will not run long enough to use with drip systems.