Jimbo --
I believe these are your typical sprinkler valves and since I believe they are in fact Rain Bird parts, I believe they are probably anti-siphon (AS) valves -- not sure how to tell a valve that is AS vs. Vacuum Pressure breaker valves (do you have a pic I could look at for one vs. the other?).. In this case, you hit the nail on the head.. My yard is higher at the far end nearest the neighbor behind me (probably at least 18-24" height difference from front to back of yard), so IF the heads could re-claim the left-over water in the pipes, that would certainly explain the problem.
hj -- the valves are not the inline model, but are the typical plastic valves you can find at your local home depot et-al. The plastic manual screw valves are tight, and I do realize that if you do open them you try out the valve, you will get some water that way..
So, since I'm interested in re-doing this mess anyway (relocating the valves, heads, pipes,etc), is it safe to assume that in this sort of situation, I should do one of the following to rectify this in the "new" setup :
- If the valves remain in their same general location (at the bottom of my "hilled" yard), ditch the underground box and raise all sprinkler valves higher than the highest sprinkler head in the system.
- If I relocate the valves (my preference) to the rear of the yard (e.g. put them at the top of the "hill"), keep the new valves out of the box as well (perhaps ~1' above grade) to avoid this sort of problem.
Also -- a few other questions.. Is there any great reason to buy one brand of valve over another brand or one style over another? As mentioned here, what are the benefits of a AS valve vs. the Vacuum Pressure breaker style of valve? Also -- I've got two large (in my opinion) chain irrigation supply places (Aqua Flo & EWing) at my disposal that have all kinds of stuff that I can't get from my local Home Depot -- in general, is the stuff that these guys carry much better in terms of overall quality than your typical Home Depot/OSH products (e.g. Toro, Rain Bird, etc) -- perhaps differences in residential grade vs. commercial grade?
Many thanks in advance.. I suspect this existing system was installed by a sprinkler person at some point in time, but I've never really looked into this underground box much since we bought this house ~3 years ago.. I guess I ought to fix this ASAP as a potential contamination issue is possible from what you're indicating -- correct (due to backflow)?