Ask The Droughtbusters: Feb. 1998

Droughtbusters is a question and answer column provided as a service to the landscape industry by the Irrigation Association and Lawn & Landscape magazine. Please fax your questions for the Droughtbusters to 800/455-4320 or e-mail them to irricom1@earthlink.net.

QUESTION:I am a landscape contractor based in the state of Washington who does principally residential landscape construction. What is the length of time generally required for a satisfactory pressure test of a residential irrigation system?

ANSWER:In your neck of the woods, pipe solvent can take more than a day to set up completely. If you follow the directions on the glue can label and wait 24 hours before pressure testing, your systems should hold pressure for two to six hours.

The problem, according to IA member Marilyn Edlund of Edlund Associates, an irrigation consulting firm in Renton, Wash., could be that contractors glue when it’s too cold or rush the pressure test. The colder it is, the longer it takes the solvent weld to set, she pointed out. Most labels say wait 24 hours to achieve full strength depending upon temperature and humidity. It’s wet and cool in Washington, and glue takes longer to set here than down South.

Edlund recommended contractors backfill the pipe, but not the joints, tees or valves. Give the system at least 24 hours before pressure testing. If there is a problem, you can find it and fix it quickly. When she conducts a pressure test, Edlund asks the contractor to pump up the system for six hours and drain it. Then pump it up again for two hours before the test begins. If the system holds for two hours after the test has started, the system has passed four hours of testing.

If the temperature drops below 40 degrees Fahrenheit, Edlund said contractors shouldn’t glue pipe. If the nighttime temperature drops below 40 degrees, Edlund recommends waiting two days before testing. I’ve seen joints push apart after 24 hours of cementing because temperatures were too cold, she warned. When it’s cold, make a special effort not to move pipe once it has glued.

Just keep in mind that cement takes longer to set in cool and wet conditions. When it’s cool and wet, finish the installation, don’t backfill joints and valves, and give the welds 48 hours if you can to set. Then pressure test.