Five zones. 15 years old. One zone only dribbles water from three rotating heads. All other zones are full pressure. Zone 1 valve opens electrically and manually with no difference in dribbling. Three heads checked and no signs of leakage at pipes directly connecting to the head. PVC pipe under house to each control valve. Black pipe with blue stripe at heads. Can hear water running at Zone 1 valve, but not enough is getting to the heads to pop them up. System was blown out two years ago, and turned on a couple of weeks ago.

Looking for ideas on how to find the likely leak or blockage in Zone 1.

This message has been edited. Last edited by: 4MUL8R,

Pop the top off that zone's valve. They sometimes get crap from the water supply clogging them up. Small pebbles or dirt often come through in our water. There's likely something on the (internal filter) screen, or something preventing the valve from opening. If you get full flow with the valve top off (you'll get wet), you know it's the valve itself or something downstream.

I vote Zone Valve

By "pop the top" with apologies to Alan Jackson, do you mean to unscrew the electric solenoid? Or, do you mean to unscrew the four screws on the perimeter of the valve?

I go with Vinnybass's suggestion. You mentioned that the system had been repaired recently? Every time you open up the plumbing, dirt and insects can get in. Remove the head from the one that doesn't flow. Let the water flow "if it can" can then clean the nozzle. I most often find that ants and similar insects are plugging the nozzle. I get rid of them by "blowing" in reverse through the nozzle. This does it every time.

Yes, the four screws that hold the top (the bonnet according to Rain Bird) on. The bigger round part, not the smaller, which is the solenoid. Under that you'll find a diaphragm, spring, & likely a little basket looking thing which acts as a filter (more like a strainer). Pull those out, check for crap & while it's apart maybe run the water through it for a few seconds. Reassemble and Bob's yer uncle. It's really pretty simple.

BTW, when re-inserting the screws into the plastic I've found it best to turn them backward a little until the screw drops into the existing thread, rather than just screwing them straight in, on the off-chance it may try to start a new thread which isn't usually good for the plastic. After all, we don't want to install a new valve if not needed.

All sound advice in the previous replies.

Definitely sounds like blockage somewhere. Start at the valve and work your way through the zone head by head. You can unscrew the head from the canister and if you have a geyser check the plastic screen/filter. No geyser, check the fitting where it connects to the head. Also keep in mind that as landscaping matures, so does the root system that you cannot see. Many times I have seen roots strangle a pipe completely closed.

-Jeff

Well what happened? Get it going?

quote:

Can hear water running at Zone 1 valve, but not enough is getting to the heads to pop them up

It sounds to me like you have a leak between the valve and the first sprinkler head.

Update: Today I opened the zone 1 valve. No debris, no clogs, no leaks, no rips in the diaphragm. Nothing that suggested a valve issue. It appears to this old valve designer (my first job) that the valve is a pilot operated control valve, and the solenoid only acts to close the pilot orifice. So, unscrewing the pilot solenoid the water flows under pressure through the valve and opens the plug with the help of the diaphragm.

I know that water is flowing to the valve. I know that the diaphragm is able to seal. I know that the solenoid o-ring is OK.

When turning the adjacent valve solenoid 1/4 turn, I can hear water flowing immediately. On the problem valve, I can turn the solenoid manually and hear NO water running. This must mean that the water cannot flow under the main diaphragm and lift the plug away from its seat. I will have to check this again, once the water level in the valve box subsides. I think I am supposed to send out a raven every so often to see how high the water is.