Low water pressure in one zone, manual valve control fixes it

[Tim in Fort Worth]

I've got one zone that frequently doesn't pop the sprinkler heads up all the way. Sometimes it does, and sometimes it doesn't I recently fixed a small leak on the threaded connection to the valve on the charged side (it's not the problem) and decided to test the manual control. I opened the manual valve a fair amount and immediately got full pressure to all the heads. Dang near popped up all the way to the next county. All the other zones work fine. So what is the likely problem? I'm suspecting the diaphragm, but I replaced the diaphragm on this valve about 5 years ago. The only other thing I can think of is the solenoid. And if it is the solenoid, is it easy to fix? Valves are relatively cheap, but after the recent leak repair I'm not looking forward to dealing with this line again. The valve is located about 12" from a T-fitting that passes water to the other valves, with the base of the T-fitting reduced and feeding the valve. I've got about 1 more cut in the PVC before I'm too close to glue on to the 3/4" pipe coming out of the T-fitting. On the outflow side of the valve it runs about 12" before a 90* fitting sends it down to a T-fitting, which runs both out to the yard and back under the previously mentioned plumbing. It really sucks to have it stacked like this with such short lengths of pipe to work with. I'd have to dig up about 10' to be able to bend the 1 1/4" PVC to use a connector. On the bright side, I used a 1" compression fitting on the outflow side, so if I have to replace the valve the only dicey part is using up more of the short length on the charged side. Thanks for any help you can give me.

 

[WorthFlorida]

Sounds like a diaphragm or there is debris inside the valve passageways. Rarely will it be a solenoid. Solenoids work or do not work. At the valve turn the solenoid about a 1/4 turn or more CCW to open the diaphragm. From this video you can see how debris line dirt or sand an plug up the dump port.

 

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[Tim in Fort Worth]

Sounds like a diaphragm or there is debris inside the valve passageways. Rarely will it be a solenoid. Solenoids work or do not work. At the valve turn the solenoid about a 1/4 turn or more CCW to open the diaphragm. From this video you can see how debris line dirt or sand an plug up the dump port.

Thanks. I loosened the solenoid until the sprinklers activated. They popped all the way up like they should. So both the manual valve knob and the solenoid will get the heads to pop all the way up. I also loosened the solenoid a second time, after I manually set that zone to run for 5 minutes. The heads didn't pop up when the manual run started, but did pop up when I loosened the solenoid and stayed up when I tightened it back down. So I'm guessing that the fix is to pop the top off the valve to check the diaphragm, and flush out the valve while it's open. It was covered in mud today, but it's a Richdel brand, but I forget the model #.

 

[WorthFlorida]

Could be a open solenoid or a wire broke at the valve. You also need to check it at the controller. With any zone activated you'll read anywhere from 18v-24v. If you don't have a voltmeter, swap the wire for the bad zone with another. An open solenoid voltage may be as high as 29v ac. If the problem is at the controller, use a spare zone and reprogram the controller. If there is no spare zones then usually you need to replace a module.

If you have a volt ohm meter, the resistance reading of a good solenoid can be from 20-60 ohms but usually it'll be around 40 ohms. I

 

[Tim in Fort Worth]

Could be a open solenoid or a wire broke at the valve. You also need to check it at the controller. With any zone activated you'll read anywhere from 18v-24v. If you don't have a voltmeter, swap the wire for the bad zone with another. An open solenoid voltage may be as high as 29v ac. If the problem is at the controller, use a spare zone and reprogram the controller. If there is no spare zones then usually you need to replace a module.

I used a meter at the controller, and the voltage was right on target (24v). Haven't checked it at the valve, but am not too keen on cutting the wires if I don't have to. It really seems like something mechanical, based on what is going on. I think the next step is going to have to be removing the top of the valve for an inspection of the diaphragm and flushing out the valve. If that doesn't work though, I'll probably have to troubleshoot the electrical situation at the valve.

 

[Tim in Fort Worth]

Looks like it's new valve time with no other choice. This morning I removed the bonnet of the Richdel R204 to flush it out and examine the diaphragm. When the bonnet was off I noticed that there was a crack at one of the screw holes on the body next to the inlet side of the valve. Not sure how it got there, but I suspect it could have happened when the ice storm came to visit Texas in February. So anything else that may have been the problem is now moot. Since Richdel is now Irritrol and I can't get the R-204 I'm going to have to examine my options on which brand and model to use as a replacement.