At startup this year, the o-ring under the bonnet of my 765 Febco was done, so I decided to replace the entire bonnet/poppet. The kit came with two o-rings, one thicker and one thinner, sized to the bonnet. I used the thicker of the two o-rings. The kit also came with a small packet of grease, I assumed that was to lubricate the o-ring.

After installing the new kit, water still leaks at the o-ring. The o-ring appears to be bulging out at the spot of the leak. I have tried loosening the bonnet, as well as making it more tight - still leaks. Doesn't appear to be anything wrong with the brass surface where the o-ring bulges. Nothing has changed over the winter with respect to the system itself, so unless the city changed the water pressure since last fall, the water pressure should be the same.

Is there something I could be doing wrong? Is the thinner o-ring that came with the kit for a smaller vacuum breaker or should I use that one instead?

Was your device subject to ANY freezing at all over the winter?

Of course it gets cold here (Colorado) but I properly blew out/winterized the sprinkler system, including evacuating the vacuum breaker of water. As I have for the last 10+ years.



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I have exactly the same problem but my valve did freeze over the winter. Replaced the guts and have the large o-ring bulge out. Did you ever have any lot with getting your valve to seal?

I have the same problem here in Michigan. Was there any solution to this problem?