I have a 3/4 inch inline automatic sprinkler valve that will not shut off, whether it is turned on electrically or by unscrewing the solenoid. It drives a drip line with about 15 heads, so the flow rate is rather low. If I close the main shutoff valve to the system and reopen it or open a drain valve downstream so the flow increases dramatically it closes fine, so it appears to depend on the downstream pressure being high. Can anyone help with the cause and fix? Normally I would just replace the valve as they are not expensive enough to fight with, but I am concerned about getting a new one in. I have unions both sides of the valve, but the pipes seem fixed in the ground. I would have to find one the same length and get the unions to mate without pulling or pushing the pipe.
Plumbing – Automatic sprinkler valve will not shut off
plumbingsprinkler-system
Related Solutions
The type of anti-siphon valve you are likely using is not intended be constantly under pressure. It is not intended to have down stream valves actually controlling flow. It is meant to only be active for the duration of an irrigation cycle, then to have pressure removed when the sprinklers are turned off.
The proper device in this situation is a reduced pressure backflow device. It is much more expensive than irrigation anti-siphon valves, but it can serve many stations instead of installing a basic anti-siphon valve for each station. It also allows more flexibility in control valve placement because you don't need an anti-siphon valve sticking up after every valve.
Yes, you could just run out and turn on the main valve before the sprinklers cycle, then turn it off when finished, but that defeats the purpose of having an automatic sprinkler system.
How do I know all this? I did the exact same thing and had the exact same problem!
I'm not sure who the idiot was who put this down that hole, but it was pretty firmly lodged in there. I cut off a bit more of the PVC and was able to get my trusty pry bar in the notch and turn it. After about three quarters of a turn the stupid thing came out. And sure enough, there was a regular stop and waste down there underneath whatever the heck this is.
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Best Answer
Opening a drain valve downstream will not raise downstream pressure, it will increase flow and lower total system pressure.
If there is any flow the valve should close, as pressure above the diaphragm equalizes with supply pressure upon closing of the solenoid pilot port.
Get the brand and model # of the valve and order a rebuild kit for it as your problem is very likely to be mechanical. Turn off the supply and remove the valve bonnet, inspect and clean internal components (flush all ports to remove debris, check the diaphragm and support rings for damage or cracks, inspect the sealing surfaces and seats). Replace the washers and diaphragm with new ones from the rebuild kit.