SPRINKLER TALK FORUM - You Got Questions, We've Got Answers

I have a Watts 800M4FR pressure vacuum breaker. When I turned it on this year it started leaking from the top, apparently between the vent float and the bonnet. Information I found online suggested that I replace the faulty parts, so I did. In fact, I bought the full replacement kit and replaced every part in it, but it still continued leaking between the NEW vent float and bonnet.

I rebuilt it two more times, even tried using the sealant paste that the parts come with between the vent float and bonnet, but it still leaks. Here's a video: http://www.youtube.com/watch?v=O-wfL-JYRWw Any ideas? Thanks.

Quoted from "Wet_Boots"

Did you use all the replacement parts? Including the large O-ring? Is this still the original cover/bonnet?

Yep, all of them. Large O-ring, bonnet and cover included.

I'm not sure if the water pressure is right. It appears to be working properly, but I suppose it might be a bit low.

The problem I see with the partially-open valve theory is that the PVB still leaks even when the sprinklers are off. My physics background leads me to think that the pressure in the PVB would equal the pressure from the main water source if the water isn't flowing, as long as the valves are at least partially open. Does that sound right?

It's hard to imagine how freeze damage could cause a leak between brand new parts, so I think your faulty part theory sounds most likely to me. Maybe I'll try parts from another vendor and if that doesn't work, hire a pro.

Thanks for your input. It's helpful to know that I wasn't missing something obvious!