SPRINKLER TALK FORUM - You Got Questions, We've Got Answers

That's a Superior 800 series valve adapter screwed into a brass valve body.
There's either a hole in the diaphragm or some debris has damaged the seat washer.
The whole unit unscrews from the brass body.
You'll want to buy a rebuild kit for the 800 series. I think what you have are 3/4 inch but I wouldn't bet my life on it. Take the adapter to the irrigation store. Ewing or John Deere. The only difference in the two kits is the seat washer. 3/4 inch or 1 inch. Everything else is identical.
First unscrew the cap. That's the big round brass thing on top of the valve on the PVC side.
Now unscrew the valve adapter from the brass body.
If you want you can just replace the whole adapter instead of rebuilding. That one there will run you about 40 bucks. The rebuild kit where I buy it is 7 bucks.
I haven't told them yet that the kit is 7 bucks and just the diaphragm alone is 12. They might have their pricing backwards.
You can get a good plastic adapter for much cheaper. Irritrol has a couple of good ones.
Be careful not to snap any pipes while unscrewing the cap and adapter. Sometime's they can be stubborn.
Good luck!

Oh yeah, you can turn on each valve with the bleeder screw to determine which valve is which. The bleeder screw is the thing that looks like you can turn it with a screwdriver. Water will come out when you turn the screw. Just keep turning it slowly til the valve comes on.

I edited your link so it would work.
Yes take that off.
Flush the line while you have it off.

I wonder how old those adapters are. I don't remember seeing those solenoids with the top nut, as opposed to a plastic keeper piece.

Quoted from "Wet_Boots"

I wonder how old those adapters are. I don't remember seeing those solenoids with the top nut, as opposed to a plastic keeper piece.

I'd venture to say the solenoids posts with the top nut have been around 15 years give or take on the Superior brand valves.

The valves adapters they sell at the Home Depot which look identical but have the Orbit name on them still use the plastic keeper.
So do the Rainbird ones that look identical. I'm not even sure if they still make the Rainbird ones.
The Champion brand valve adapters sill have the plastic as well I believe.

Quoted from "mrfixit"

Quoted from "Wet_Boots"

I wonder how old those adapters are. I don't remember seeing those solenoids with the top nut, as opposed to a plastic keeper piece.

I'd venture to say the solenoids posts with the top nut have been around 15 years give or take on the Superior brand valves.

The valves adapters they sell at the Home Depot which look identical but have the Orbit name on them still use the plastic keeper.
So do the Rainbird ones that look identical. I'm not even sure if they still make the Rainbird ones.
The Champion brand valve adapters sill have the plastic as well I believe.

Thanks. I only used the Superior/Champion combination one time, more than 20 years ago, for a client that wanted all brass and copper for the exposed plumbing. Turns out the 800 adapters had O-ring issues with the flow control shafts. Might have been damage from freezing water that didn't exit that area of the valves during winterizing.