Backflow preventer acting weird

BigRob

Hey all, I usually keep the make-up water to our hydronic system shutoff. After flushing the mag filter a couple times I opened the fill shut off valve and all of a sudden the back flow preventer started dumping from he vent. Pressure is lower on the boiler side; about 15psi. It's strange because if I close the back flow preventer outlet isolation valve and open the inlet valve, water dumps from the vent, but not vice versa. So water is traveling from the inlet to the vent. I removed the vent plunger and everything seems fine.

Any ideas?

Jamie Hall

Make and model of backflow preventer? On most reduced pressure backflow prevention devices, the vent is part of the pressure reducing section -- and flow from that indicates that the valve is not seating properly. Some of them can be repaired. Some can't.

BigRob

Jamie Hall said:

Make and model of backflow preventer? On most reduced pressure backflow prevention devices, the vent is part of the pressure reducing section -- and flow from that indicates that the valve is not seating properly. Some of them can be repaired. Some can't.

It's a 1/2" Watts FL009QT. The spring opens the valve, so I guess there is not enough pressure pushing down on the diaphragm?? I don't see how that could happen.

ratio

Around here, backflow preventers have to be inspected/serviced yearly by a licensed technician. There's a week long (iirc) class & a test to get the license. It might be quicker just getting someone to service it for you, especially if you're going to have to call in someone to tag it anyway.

Jamie Hall

Springs get weak. Diaphragms tear. But @ratio is right -- it's best to get someone who knows these things to repair and tag them.