Monday, March 10, 2014

Problems With My Pressure Vacuum Breaker

Hi folks! I recently purchased a 6 year old home with an irrigation system. The system never worked because there was too much sediment coming from the well and the home owner decided not to use the sprinklers. I had a sediment filter installed shortly after moving in and the irrigation system worked OK. However, after every other cycle or so, water would just rush out of my Febco 765 PVB. If I shut the water supply and restart it the PVB seemed to work again and the sprinkler system would go through another couple of cycles but then the problem would come back. I thought that the PVB was at fault so I replaced my Febco 765 for a Toro 53300 PVB. Alas, I am still having the same problem with the Toro. I already have a pressure tank between the well and the sediment filter that was installed at the same time as my whole house filters (sediment, aeration and softener). When the sprinkler system shuts down, however, I always hear the aeration filter running. Would that have anything to do with my PVB problem, possibly creating low pressure on the filter side of PVB? If so, how would I fix it?

It sure sounds like a pressure problem. It is doing what it is supposed to do when there is low pressure.
Was the device tested by a qualified backflow tester? This is kind of important for a couple of reason that we do not need to discuss now. The main purpose of testing would be to actually test the loading on the spring that holds the vent in place. This would tell you if the valve itself was actually working as it should.
Once this is determined, then look at pressures on both sides of the valve. From reading what you wrote, it dumps water, you reset the pressure by shutting of the supply. This will allow some water to enter the sprinkler side, you then repressurize, and everything works as it should.Your pressure would be more or less uniform throughout your system. Bump pressure up, PVB doesn't see pressure drop or loss, works like it should. Pressure drops on supply side for any reason below sprinkler side, water dumps.
I'd look at the filter you have in place and I'd also look at the flow rating of the sprinklers.
There is a great site mentioned here from time to time on yard sprinkler systems.
Probably the best site for yard sprinklers on the internet. You may want to look at this site for some ideas.
Good luck with your project and more questions, ask away and someone will help you.

Whoa! Jess's site is amazing! After spending a bit of time reading up on PVB's, I see that mine is installed about 10 feet lower than some sprinkler heads and valves. Could be my problem right there! I know who did the original install so he's getting the first call tomorrow morning! Thanks for the help and I'll post the final resolution when I get it.

Tags: pressure, irrigation system, sediment filter, sprinkler side, sprinkler system