Leak from PVB on Backflow Preventer
#1
05-08-20, 11:00 AM
Leak from PVB on Backflow Preventer
Have a slow leak on my backflow preventer.
I replaced the bonnet and added a new o-ring, but I still have some slight seepage coming through.
Any idea what could be causing this? Would plumber's grease or a silicone sealant on the o-ring and threads of the bonnet help?
I replaced the bonnet and added a new o-ring, but I still have some slight seepage coming through.
Any idea what could be causing this? Would plumber's grease or a silicone sealant on the o-ring and threads of the bonnet help?
#2
05-08-20, 10:26 PM
Group Moderator
Doubtful grease would help.
Not sure I'd want any type of sealant like that inside the valve.
Post the model number off its tag.
Not sure I'd want any type of sealant like that inside the valve.
Post the model number off its tag.
#4
05-09-20, 09:07 AM
Group Moderator
I was looking at the construction. The valve is bronze and the bonnet is plastic or bakelite. Not likely there's a problem with the casting which leaves the o ring or the actual bonnet as the problem.
You could try some vaseline or plumbers grease on the o ring.
Your next step would be to try another o ring and then replace the cap if the leak is still there.
You could try some vaseline or plumbers grease on the o ring.
Your next step would be to try another o ring and then replace the cap if the leak is still there.
#5
05-09-20, 09:17 AM
A few wraps of teflon tape on the threads would also not hurt but it is the Oring that should do the sealing.
I am with PJmax on greasing the Oring. This should help prevent it from deforming when tightening/compressing..
I am with PJmax on greasing the Oring. This should help prevent it from deforming when tightening/compressing..
#6
05-09-20, 09:56 AM
Member
Any chance it was left out and froze? I have seen several of those, that plastic cage holds the valve asm and the plastic can crack. Take it out and inspect, they are cheap to replace!
#7
05-09-20, 09:58 AM
Group Moderator
There is a plastic assembly inside but the problem is the bonnet cover is leaking.
Possibly the plastic bonnet is distorted from freezing.
Possibly the plastic bonnet is distorted from freezing.
