Mystery solved. I finally got a chance to disassemble the valve and there was a small rock on the ledge where the diaphram seals. It was just large enough to keep the valve open once it was opened by the solenoid but when I closed the downstream mechanical valve the flow was stopped and the diaphram would reseal. Any larger and the valve would never seal and any smaller it would have gone unnoticed. Obviously Rainbird gave me bad info because the valve works just fine now. Thanks again for the s...
Thanks for the responses. The negative pressure is never relieved, i.e. the water in the line apparently keeps the valve open by suction which releases more water which keeps the valve open, etc. and the valve never closes (water continued to flow overnight after power was removed). I thought about putting a drain valve in-line right after the 100-DS but wasn't sure how the dynamic would work. I think the suction might pull it open and allow air into the line breaking the suction. I will try thi...
Thanks for the responses. The negative pressure is never relieved, i.e. the water in the line apparently keeps the valve open by suction which releases more water which keeps the valve open, etc. and the valve never closes (water continued to flow overnight after power was removed). I thought about putting a drain valve in-line right after the 100-DS but wasn't sure how the dynamic would work. I think the suction might pull it open and allow air into the line breaking the suction. I will try thi...
I have a line with a long downhill run and a 100-DS valve at the top. When power is removed the valve doesn't close. I called the 1800RAINBIRD line and he confirmed my guess that negative pressure is preventing the line from closing. He offered no advice. Anyway, being an engineer, I could design a circuit with another valve that would open momentarily when power is removed to break the suction long enough to let the valve close but hoped there might be a ready made solution. I thought maybe it ...
