Drip irrigation is one of the most efficient ways to water the home garden. The slow rates of water application reduce water loss through evaporation and runoff, and the ground-level water application reduces the risks of foliar diseases that can be spread by splashing water.
There are many, many systems and uses for drip irrigation out there. CSU Fact Sheet 7.402 gives a great overview of the range of options and considerations for each. This flexibility is an advantage of these systems, but the options for equipment and design can be overwhelming if you’re starting from scratch. This post will take you through the basic equipment from water source to garden using an example system based on my own garden. So you can follow along, here are the assumptions I'm working with: This is an add-on system, designed for a home vegetable garden, using municipal water from an outside faucet as a water source. In the garden, I’ll use 1/4 inch drip tape, also called drip tubing, drip line, or emitter tubing.
Drip line is polyethylene tubing with emitters, where water is dispensed, at regular intervals. Typical emitter spacings for 1/4 inch tubing are 6 inches, 12 inches, and 24 inches. Emitters that are spaced up to 12 inches apart can provide consistent moisture along the drip line.
|Photo by Penn State Extension|
If you’re using an outside faucet as your water source, you can add a Y-connector and reserve one side for a garden hose. The faucet will serve as the valve and can be opened and closed manually, though automated controllers are also available.
Next, you’ll want a backflow prevention device. These devices allow water to flow in one direction only, which prevents contamination of potable water. This is especially important for drip systems because they lie on the soil surface and can be used for fertigation, both of which are potential sources of contaminants. A good first step in selecting a backflow prevention device is to contact your local water provider, as many municipalities have minimum requirements for backflow prevention devices. The most simple and often cheapest option is an anti-siphon device, also called an external or hose vacuum breaker. As their names indicate, these devices prevent backflow due to siphoning (vs. back pressure). For this minimal backflow prevention approach to be sufficient, make sure you’re using an above-ground connection to the water source located 6-12 inches above the height of your emitters.
|Rainbird Faucet Connection Kit|
Next in line is the filter. Even if your emitters are clog-resistant, a filter will increase the longevity of your system. If you’re using municipal water sources, 150-200 mesh filters are usually sufficient. The higher the mesh count, the greater filtration provided.
|Photo of Y-shaped mesh filter by Berry Hill Drip|
The faucet connection kit pictured above has an inline mesh filter pre-installed within the backflow preventer. While these kits are simple to set up, you’ll need to disassemble them to clean the filter. A Y-shaped filter (right) allows the filter alone to be removed for easy cleaning or replacement.
|15 psi pressure regulator|
Next in the assembly is a pressure reducer, also called a pressure regulator. To select an appropriate pressure regulator, first determine the ideal pressure for the drip line and other components you’ve selected by checking details from the manufacturer. Then, keep in mind any elevation changes from water source to emitters. For every 10 feet in elevation gain in the downstream direction, add 5 psi (pounds per square inch) to your desired pressure.
On the left side of the pressure regulator pictured here, 15 psi indicates the water pressure downstream of the pressure reducer; this number should match the desired pressure for your drip line. On the right side of the pressure reducer, 1/10 - 7 gpm (gallons per minute) indicates the required flow rate for this particular device.
In a home vegetable garden set-up, you’ll likely want multiple drip lines that will correspond to multiple rows of plants. In this case, a header line that feeds multiple drip lines will be connected to the downstream end of your pressure regulator. To connect the header line, you’ll need an adapter, which come in a range of sizes.
|Adapter for connecting to 3/4" thread to 1" header.|
A typical adapter for this set-up is threaded on one end to fit the pressure regulator; the other end of the adapter is inserted into your header line and secured with a clamp. For a home vegetable garden using 1/4 inch drip line, 1/2 inch polyethylene tubing is usually sufficient for the header, but 3/4 inch and 1 inch tubing is also available.
Finally, you'll need to connect your drip line to the header. You may be able to find 1/2 inch header tubing that has holes at regular intervals that work for your layout; if your tubing is thicker than 1/2 inch, or the available intervals don't work for your design, you can use a hole punch, often called a punch gun, to make holes in the header at your preferred intervals, and use couplers to connect the drip line to the header. One end of the coupler should be fitted to the hole you punched in your header, and the other end should be fitted to your drip tape (1/4 inch in this scenario). Couplers are available with or without valves and can be used as inline connections as well. If you've ever made the mistake of forgetting to install a pressure reducer, you've probably had your drip line burst. When replacing the drip line isn't practical, the damaged section can be snipped out, and a coupler can be used to repair the line.
These basic components and flow (water source, valve, backflow preventer, filter, pressure reducer, header tubing, and emitter tubing) are the foundation of any drip system, but there is room for great variation. If you're thinking of making the change from hose-dragging, here are some additional resources:
Planttalk Colorado 1621: Watering Colorado Soils
CSU Extension Fact Sheet 7.402: Drip Irrigation for Home Gardens
CMG Garden Notes: Watering Efficiently