View Full Version : Watts Backflow Preventer leaking from vent

01-21-2010, 02:12 PM
On the supply to my Furnace there is a Watts 1/2" 9D-M3 Backflow Preventer With Atmospheric Vent just before the pressure regulator. The backflow preventer has been leaking from the vent at the rate of about 2 drops per second. What's the cause and what's the cure?

Peter Griffin
01-21-2010, 04:44 PM
Backflow preventers leak because there is a backflow situation. Or was a backflow situation and now there is some crap under the seat.

01-23-2010, 07:17 AM
Furnaces are hot air heaters so why do you even have a water supply to it. IF it is a hot water boiler, they usually do not need a BFP since the feeder/relief valve performs that function. However if the BFP is leaking it could be because there is a backflow, which is not likely (since the boiler pressure is LESS than the supply line so any leakage would be in the opposite direction and would cause overpressure in the boiler), or the valve has failed and needs replacement.

Peter Griffin
01-23-2010, 01:42 PM
code now requires a backlfow preventer on hydronic boilers. Usually it is in the form of a Watts 1156F-9D combination. And yes, because boiler system pressure is generally around 15 lbs, there has to be an extreme loss of pressure on the supply side for backflow to occur, plus, the S1156 feeder has a check valve in it also so the usual cause is crap under the seat of the 9D or the valve seat on the 9D is bad.

06-30-2011, 07:33 PM
My church has a backflow preventer leaking i was going to straight pipe it and then i thought they might be tied in by a recirc line and i needed at least a check valve to prevent backflow but should i just replace the check valve do you think the vent will continue to leak and i notice some backflow preventers without a vent hole which one should i get

06-30-2011, 08:35 PM
You might want to post a picture so we can "see" what you have there.

800 pixels or less.