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

What is your water pressure? Sometimes if your pressure is low enough, the backflow device may think there is a backflow condition and not seal properly. Also, sometimes if you open the inlet valve too slow the valve will not seat properly. Try closing and opening it a couple of times to see if it seats properly. Was the system properly winterized? If need be, you can replace the internal parts of the 765.

I haven't had many problems out of the Febco backflows I have installed, but I have seen the problem you are talking about before. You should be able to get your water pressure reading either a) from a gauge near your well holding tank, or b) if you are on municipal water, from the water department. You could also hook a pressure gauge onto a hose bib on the outside of the house. There many not be any cracks in the brass, but the inside diaphragm may have a tear or crack in it. You have to remove the hex nut on top of the backflow to remove in internal components of the backflow, check that out, and replace it if need be. If the outside "s****" so to speak of the backflow is OK, then just inspect the internal components of it, and replace if need be. Also, I am assuming the drip is coming from undernieth the bonnet, correct?

Your correct, you can buy a replacement kit for just the internal components