Leaking sprinkler valve

I have two leaking lawn sprinkler valves: one is moist at the valve-to-pvc connection and the other is dripping solid at the valve-to-pvc connection. Is there a recommended way to stop these leaks (silicone?) without cutting out the valve, re-seating and re-cementing onto new piping? I have placed a mirror underneath and see no visible signs of hairline cracks so I assume the moisture is coming from the connection itself. Thanks in advance.
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the valve out and use pipe tape on the threading. It doesn't look like any tape was used previously and is likely the reason it is leaking now. I was trying to avoid this as both valves are inline with one feeding into a Tee at each end with different sized pipes branching off. It will take some major surgery but I guess I have a three day weekend coming up.
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I fixed mine by just cutting the leaking side, and putting it back together with a PVC union. A union on both ends of the valve is nicer, but I only needed to fix one end. :)
You can thread pvc schd40, but thinner stuff not so much. You can get a cheap pipe threading kit for 1/2", 3/4" and 1" pipe from harbor freight when it comes on sale.
Or as I did, buy two unions, one for threaded and one for slip, and mix and match so that the valves each get a threaded half, and the pipe gets the slip half glued on. A short threaded nipple connects valve-union.
sdb
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