When a lawn or garden sprinkler head is not turning off, still leaking water when it should be off, it may be due to debris inside the valve or because the diaphragm (rubber gasket) inside the valve is damaged. If the diaphragm is torn or damaged, it will not be able to stop all of the water so the sprinklers will not turn off. You may try to clean it first. For an old valve, the gasket may be worn out already so cleaning will not work. We will show two different ways to fix it, either rebuilding it or replacing it. Rebuilding is cheaper and requires less time than replacement.
Rebuilding is a fairly common sprinkler valve repair, and rebuild kits are available for many valves. It is a good idea to have a rebuild kit ready before opening the valve, just in case many parts need replacement. This method has its advantages, brass is more resistant to chemicals and less susceptible to failure due to cracking. Brass also has longer life because plastic degrades over time in extreme environments and in direct sunlight.
If you decide to replace the valve, you should purchase a replacement anti-siphon valve that is the exact same size as the old one. However, if you’re unable to find a replacement that is the exact same size, you may be able to use various PVC couplers to help match up an anti-siphon valve that uses a PVC pipe or galvanized steel pipe of a different size. Attaching PVC pipe to fittings with PVC cement is super easy. If your pipes are galvanized pipes, then be aware there are extra precaution to be taken as shown in the video.
Check out “How to Shut Off Main Water Supply Valve Without Special Tools” https://youtu.be/fubzxXqHQHo
Index
0:00 How do I know if my sprinkler valve is bad?
0:30 method 1: rebuild with repair kit (brass)
0:54 loosen screws for valve, remove anti siphon cap
1:24 remove valve
1:51 match many washers, o-rings & gaskets
2:53 put valve & anti-siphon cap back
3:46 method 2: replace brass with PVC valve
4:06 difficult to cut brass valve
4:43 problem: new valve is wider than 2 pipes
5:03 PVC may break
5:32 Teflon tape: metal & PVC
5:53 Attaching PVC pipe to fittings with PVC cement
6:16 need both level & distance correct
7:13 leaks underground
8:02 valve must be 6-inch higher than any sprinkler heads https://twitter.com/RealGeniusAsian/status/1446253052751540234