Question
Hello Jeff,
We recently purchased a home with an irrigation system already in place. We
have a large slope in the backyard which is being served by three circuits. All
circuits have anti-siphon style valves installed, however, the height of these
valves is between 3 feet for the lowest circuit, all the way to 20 feet below the
sprinkler heads (at the top of our slope. Our home is at the base of the
slope). What we have been reading through our research is that the valves are
supposed to be at least 6 to 12 inches above the highest sprinkler head. With
the lines already in the ground, and all of the electrical lines already run to a
central location, is there anything we can install inline to stop the water from
draining out of the anti-siphon valves after the circuit has been turned off. It
drains for a good 30 minutes! Do we need to use a different style valve for
use on a hill? Thank you in advance for your time and for any advice you can
provide!

Answer
Yes, you can install check valves inline that will prevent backflow.  They should be available where irrigation products are sold, but if you have trouble locating, look for an irrigation supplier in your area who sells to contractors.

Follow this link for a picture of a PVC check valve:

http://www.lowes.com/lowes/lkn?action=productDetail&productId=79647-34146-P32S&l...