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Mixed use zone valve sticking

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Awyo

Unregistered

1

Tuesday, July 1st 2014, 9:51am

Mixed use zone valve sticking

Zone 1 has three rotor heads and downstream of those a 25 psi regulator, poly that necks down to 1/2" feed line and then a number of drip emitters coming off of that to water a row of bushes. Life was good, the bushes get enough water with the regular watering cycle, and it saved me from digging a new separate zone through our concrete like soil.

However, now this zone's valve sticks open 90% of the time it comes on. The valve is new (less than a year old).

What I've tried:
1- cleaning valve, reassembling
2- changing order valves turn on
3- turning the bleed screw so it's open only as far as necessary

What finally shuts valve off:
If I knock on or give a gentle shake to the valve manifold, the valve generally closes. If I turn off the main water valve in the house, and then turn it back on, the valve REMAINS open and the zone starts spraying again. Only the knock or shake works.


Something I find curious:
Since the drip emitters are below my valve manifold, the drippers siphon out the water from the poly after the zone shuts off. Not sure if that makes a difference. Part of me says it shouldn't matter, since even if I had a dedicated zone for the drip system, it'd still result in a siphon. However, I've read air bubbles can cause valves to stick open, so that's what has me concerned.


Any ideas or things to look at specifically? Thanks.

mrfixit

Moderator

Posts: 1,510

Location: USA

2

Tuesday, July 1st 2014, 4:16pm

Did you mean that you have the flow control open as far as necessary and not the bleeder screw? I'm assuming you did. If not that could be a problem.

Yes the flow control should be turned down as low as you can get it and still have the sprinklers function properly. I usually turn it down until it starts to impeded the flow of water then open it back up a bit. Maybe 1/2 to a full turn.

The drip at the end of the line wont be a problem with the valve at all.

The valve probably needs a new diaphragm.

Awyo

Unregistered

3

Tuesday, July 1st 2014, 8:37pm

I did mean flow control, yes. I have it opened maybe 1.5-2 turns more than I need. I may turn that down to see if that helps. I tore the entire thing apart again, rinsed it all out. I didn't see any sediments or anything. Everything I inspected appeared to be in good shape. If this doesn't fix it, I have a spare valve and I guess my next step is swapping it out with my spare.

Thanks for your reply.

irrigirl

Unregistered

4

Wednesday, July 2nd 2014, 4:30pm

Diaphragm

:P Probably diaphragm like Mr Fixit said. I would take that diaphragm from your spare valve and swap that out first. If that doesn't work then you probably will have to replace whole valve.

irrigirl

Unregistered

5

Wednesday, July 2nd 2014, 4:32pm

Valve

Also, if your valve is pretty old, you could have a rusty solenoid plunger.. that would be another cause of sticking!

Awyo

Unregistered

6

Thursday, July 3rd 2014, 6:20pm

After another valve tear down and rebuild, it's cycled normally twice. I again didn't see any dirt or sediment, and no damage, and I replaced no parts, so I'm a bit flummoxed. Thanks for the replies.

mrfixit

Moderator

Posts: 1,510

Location: USA

7

Friday, July 4th 2014, 3:43am

Hey Awyo. What are the make and model number of the valves? If you don't know maybe you could post a picture.

I still suggest that you need new diaphragms. But without knowing which valve we're talking about that's all the help I can give you. You said yourself you've made no repairs to the valves. You've just cleaned them. Old diaphragms might look good visually but they're too stiff to function properly.

Irrigril suggested the plunger might be rusty. That's possible too. There could also be rust on the metering pin but you should have seen that when you had the vavle taken apart.
I've seen the white plastic solenoid plunger retainer keep valves from shutting off a handful of times.

We need more info. Make and model.

Awyo

Unregistered

8

Friday, July 4th 2014, 5:39pm

The valves are Rainbird 100PGA-B. I swapped out my troublesome valve for the spare I had. I'm going to be on vacation and didn't want to return to a swamp. The price of a new diaphragm appears to be about 2/3 the cost of a whole new valve, so it may be more practical to just get a whole new valve.

How does that white retainer prevent valves from shutting off? Dirt, misshapen, damage?

mrfixit

Moderator

Posts: 1,510

Location: USA

9

Friday, July 4th 2014, 6:19pm

[/quote] How does that white retainer prevent valves from shutting off? Dirt, misshapen, damage?[/quote]

No there's isn't any debris. It's a design flaw. The plunger gets caught on the white retainer and it wont close. I haven't seen it on the newer solenoids with the larger plungers. I've only seen it on THIS solenoid.

I always pull that plastic thing off and toss it.

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