Question
This pertains to a previous question pertaining to adequate GPH flow - -Will an old valve diaphragm restrict flow? Quest #2 -Regarding 1 and 2 GPH emitters, what water pressure are they designed for? Quest #3 - Backflow Preventor. I understand the main purpose for this item. This is a brass preventor, 30 years old. In the past, If I turned the main Irrigation line off and then turned it back on a little later, I would see some water come out of it for a few seconds just prior to the pressure building up, which I think is normal. Lately, I don't see any water discharge when the main valve is turned on/off. Does this need maintenance or replacement? Also, in a previous question regarding "hammer" I hear one loud bang noise in the house when one of the individual Irg. valves turns off. Is this backflow Preventor contributing to this bang because it is not releasing pressure? As you can probably tell from this question and some of my previous questions, I am having a few small problems with flow and bang noises, which I am addressing each one by process of elimination. As always, thank you in advance for your help.

Answer
Hey Bill, yes, as the diaphragms wear out, they will start restricting the flow through the valves, and eventually stop working altogether. Normally emitters will need between 20 to 30 PSI, but as far as putting out exactly 1 or 2 GPH, they will probably never put out an exact amount, but will be close. In your Febco 765, there is a poppet and seat assembly that can be replaced, but you will not always get water shooting out of the top when you turn it back on. As long as it isn't leaking water all the time, then the unit is probably working correctly. The vacuum breaker does not release pressure, what its purpose is for, is to not allow any water from the sprinkling system, to get back into the main water line and contaminate it. You might try turning down the flow control on the individual automatic valve that is giving you a bang noise when it turns off. Normally when the bang happens, it is because the valve is putting out a tremendous amount of water, and the valve is turning fast and slamming the water. Good luck and have a great day.