Backflow valves

[gahlen]

I replaced a broken irrigation valve today ( the kind that needs a t-handle to open/close ) it is 4.5 feet underground. The irrigation valve was replaced because it was stuck on. I noticed that after hooking everything back up that when I open the valve to allow water to thru the sprinker system all is as it should be. The question comes because when I close the valve, a large volume of water drains back thru the drain hole in the irrigation valve. I thought that the double backflow valves prevent back flow/siphon? Do they only operate under pressure? How can I check them and ensure that they are operating correctly?

[jimbo]

Not clear on your setup. If you are using pressure vacuum breakers or anti-siphon valves, these must be above ground and higher than any head on the system. If not, you will get drainage of the upstream piping.


I believe that RPZ valves must also be above ground. If you are using simple dual check valves, I believe this is not allowed by code.

Please post some pictures, of describe the valves involved and where they are all located.

[hj]

They do prevent backflow, but when pressure is released on them the inlet port opens as part of the protection feature, and then all of the water between the BFP and the drain valve will flow out.

[gahlen]

Here you go. The left goes to the irrigation valve which is tee'd off of the mainline from the pump to the house. The right goes to the sprinker system with solenoids and heads. This setup is lower than the highest head.

[jimbo]

I can't tell from you picture if this is underground in a pit. I checked the installation instructions for Watts double check valves and RPZ and neither should be installed where they could ever be underwater in a pit. The recommended installation is minimum 12" above ground level.


Please note that in almost any jurisdiction, backflow prevention devices can be serviced and tested ONLY by certified technicians.

[gahlen]

I have someone coming to test it this week. If there is a problem, what would you replace them with? Yes they were installed in a valve box at ground level. All of this was done by the previous owners. I want to install what is correct and what will work. I don't need a $300.00 solution when a $20.00 one will work just fine.

[Dunbar Plumbing]

I don't need a $300.00 solution when a $20.00 one will work just fine.


And one thing is for sure, you won't get away with spending $20.00 when someone comes over to test. Parts for those assemblies are not cheap by any means.

Backflow assemblies must be tested when initially installed, whenever they are moved, and once a year. It looks like a DCVA from the picture but if it is a RPZA then it is totally incorrect how it is placed. That discharge port is buried in the dirt and provides an inevitable cross-connection. GOOD LUCK

[Bob NH]

The utility often checks the backflow prevention valves. They consider it a cash cow because it takes them about 10 minutes and they charge $75 for a residential unit around here.

You could probably relocate it above ground and then get them to check it.

If you are in an area where things freeze, you need to be able to drain it with the rest of the system.

[Gary Swart]

My backflow looks similar to yours. It is mounted in a control box that is below the level of the ground and this is perfectly acceptable. I do remove it in the winter, but draining should be sufficient to keep it from freezing. I have to have an annual inspection that is done by inspectors that have city approval. It costs $25. It could be yours has a broken spring or other malfunction that will be determined by the inspection. In 22 years of my system's existance, I had to replace this valve once. I don't recall how much it was, but is sure wasn't $300!

[Terry]

Here is a nice article on back flow and why we need it.

http://www.wattsreg.com/pro/divisions/backflowprevention/learnabout/learnabout_usc.htm

http://www.wattsreg.com/pdf/F-sbn.pdf