Green Thumb: Understanding your drip irrigation system

You have just moved to Arizona, and after settling in and starting to enjoy our beautiful climate, go out to your backyard and see a stream of water shooting five feet into the air.

Or you see some plants in your yard drying out while others a few feet away are doing fine.

The only parts of the irrigation system visible are a timer box inside the garage and a number of thin tubes rising out of the ground. There is no manual for the timer.

There is no landscape map of the irrigation lines.

Welcome to the wonderful world of landscape irrigation.

The Green Valley Gardeners seminar on Nov. 6 at the East Center is an overview of Drip Irrigation System Components and will provide background information of these hidden fixtures.

Water Flow and Pressure

The drip irrigation system distributes water from the home water supply, either from the local water company, a private well or from tanks of rain harvested from storms to meet the water needs of landscape plants.

Water flow and pressure vary greatly depending upon the source, your location, and the condition and age of your irrigation system.

Pressure in the utility water mains in Green Valley has been measured from 125 psi (pounds per square inch) to 55 psi.

Drip irrigation emitters perform best with pressures between 20 to 30 psi.

Several water line pressure reducers allow both home appliances and the drip irrigation system to function properly.

Pressure vacuum breakers prevent the flow of irrigation water back into the home water supply if there is sudden decrease of water pressure.

Timers

Controllers or Timers are adjusted to run for a given length of time (duration) and after an interval of time (frequency). The duration can be from a few minutes to several hours.

The frequency can vary from minutes, hours or to days to meet the varying watering needs throughout the year.

All controllers run on electricity, using either home AC power or batteries.

The controller or timer sends a signal to open and close valves to allow water to run into the irrigation system.

Some controllers can be mounted on a tap or faucet and combine the controller and Valve into a single compact unit.

Poly Tubes and Emitters

In much of our area, the underground part of the system consists of half-inch flexible black polyethylene tubes (poly) with slip connectors and tee’s to connect side lines off the main line.

Small barbs are inserted into the tubes to connect a qu‘arter-inch spaghetti line to an emitter at the opposite end of the line.

The emitter is placed near a plant to drip water onto the root area.

A newer system uses rigid PVC tubes for the main and lateral lines, with risers at tee’s along the length.

Lines and connectors are cemented together. Emitters are mounted at the top of the risers. Spaghetti tubing delivers water to the plants.

A combination system takes advantage of the strengths of both materials, and uses PVC underground and poly above the ground.

Emitters are the final component and deliver water directly to the plants. They come in a number of varieties - low and high flow, pressure and non-pressure compensating, fixed and variable flow, single and multiport.

Emitters are rated by the water flow per hour, either in gallons or liters. Fixed flow emitters are color coded to identify the rated flow which is not specifically marked on the emitter.

Whenever possible, use pressure compensating emitters as the flow rates for the low flow and compensating emitters vary greatly with water pressure.

Please join us on Thursday morning and learn more from our speaker, Reg Kahrimanis, about those hidden components between the Timer and those little lines sticking out of the ground in your yard.

Reg is a Master Gardener, class of 2004, and has given a number of talks on irrigation and gardening in the southwest to social and civic groups in the Green Valley area.

He is also in charge of the irrigation system at the U of A Cooperative Extension garden located at 1100 White House Canyon Road.

The office at that location is manned by Master Gardeners and is open Monday through Friday from 8 a.m. until noon.

The Green Thumb articles are prepared by members of Green Valley Gardeners with the help of seminar speakers.