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tmostad

New Member

1

Monday, June 30th 2003, 1:12pm

Negative pressure prevents valve closure

I have a line with a long downhill run and a 100-DS valve at the top. When power is removed the valve doesn't close. I called the 1800RAINBIRD line and he confirmed my guess that negative pressure is preventing the line from closing. He offered no advice. Anyway, being an engineer, I could design a circuit with another valve that would open momentarily when power is removed to break the suction long enough to let the valve close but hoped there might be a ready made solution. I thought maybe it would be possible to increade the spring tension in the valve to help it close better. Please don't tell me I am an idiot for designing and installing my own system and making a simple mistake. The Rainbird hotline guy already did that.

PS - I am fully prepared to replace the valve with a different/better one if necessary.



Edited by - tmostad on Jun 30 2003 6:17:44 PM

drpete3

Supreme Member

Posts: 375

Location: USA

2

Tuesday, July 1st 2003, 7:59am

How long does it take for the valve to close?(when is the negative pressure relieved?)
What if you were to put a harmony drain at the top of the hill with the drain up side down and above ground. My thought is that this might work like the little opening on the back of a five gallon gas can and relieve the neg pressure.

Thanks,

Pete

Rays Sprinklers

Supreme Member

Posts: 493

Location: USA

3

Tuesday, July 1st 2003, 12:28pm

Hey,
I did some research with rainbird. Its funny because when i caleld as a contractor (im regestered with them) they gave me tons of advice, but then i caleld as a homeowner and didnt get as mch, i guess it depends on the person. First, is the valve 12" above the highest sprinkler heads?? is the manual bleeder closed all the way? is the soloniod closed all the way?? The negative pressure should cause that. OPen the valve clean it, make sure there are no tiny holes in the diaphram, and flush the lines. It may just be a bad valve. Assuming this isnt a 1 zone system, do the other valves to this??



Thanks
Ray
Rays Above and Beyond Automatic Lawn Sprinklers
Thanks
Ray
Rays Above and Beyond Automatic Lawn Sprinklers

Rays Sprinklers

Supreme Member

Posts: 493

Location: USA

4

Tuesday, July 1st 2003, 12:30pm

Sorry, it should say the negative pressure SHOULD NOT cause that

Thanks
Ray
Rays Above and Beyond Automatic Lawn Sprinklers
Thanks
Ray
Rays Above and Beyond Automatic Lawn Sprinklers

tmostad

New Member

5

Thursday, July 10th 2003, 10:00am

Thanks for the responses.

The negative pressure is never relieved, i.e. the water in the line apparently keeps the valve open by suction which releases more water which keeps the valve open, etc. and the valve never closes (water continued to flow overnight after power was removed). I thought about putting a drain valve in-line right after the 100-DS but wasn't sure how the dynamic would work. I think the suction might pull it open and allow air into the line breaking the suction. I will try this if all else fails.

The valve is *far* above the highest sprinkler, about 60 feet.

I know the valve is fully closed, i.e. turn so it is not manually on. There is no leakage at the valve therefore I don't think the bleeder valve is open but will check. I have 15 other valves in the system and none exhibit this behavior but also none of them are in this uniques situation. I will diassemble the valve and clean it/check the diaphrams and screens.

The guy at Rainbird was emphatic that I had made a grave mistake and implied I should have hired a contractor to do the work and was really stupid for not having done so. It was really a quite amazing conversation.

Thanks again for the suggestions.




tmostad

New Member

6

Thursday, July 10th 2003, 10:02am

Thanks for the responses.

The negative pressure is never relieved, i.e. the water in the line apparently keeps the valve open by suction which releases more water which keeps the valve open, etc. and the valve never closes (water continued to flow overnight after power was removed). I thought about putting a drain valve in-line right after the 100-DS but wasn't sure how the dynamic would work. I think the suction might pull it open and allow air into the line breaking the suction. I will try this if all else fails.

The valve is *far* above the highest sprinkler, about 60 feet.

I know the valve is fully closed, i.e. turn so it is not manually on. There is no leakage at the valve therefore I don't think the bleeder valve is open but will check. I have 15 other valves in the system and none exhibit this behavior but also none of them are in this uniques situation. I will diassemble the valve and clean it/check the diaphrams and screens.

The guy at Rainbird was emphatic that I had made a grave mistake and implied I should have hired a contractor to do the work and was really stupid for not having done so. It was really a quite amazing conversation.

Thanks again for the suggestions.




drpete3

Supreme Member

Posts: 375

Location: USA

7

Thursday, July 10th 2003, 11:24am

Another thought that I had was to use an antisiphon valve. I am not sur exactly how they work but I Know that rainbird makes one and I am using them. I am just not sure if they will relieve the neg pressure.

Thanks,

Pete
Thanks,

Pete

Rays Sprinklers

Supreme Member

Posts: 493

Location: USA

8

Saturday, July 12th 2003, 11:24am

If none of that works, try installing check valves on those heads for that valve


Thanks
Ray
Rays Above and Beyond Automatic Lawn Sprinklers
Thanks
Ray
Rays Above and Beyond Automatic Lawn Sprinklers

tmostad

New Member

9

Tuesday, July 15th 2003, 4:33pm

Mystery solved. I finally got a chance to disassemble the valve and there was a small rock on the ledge where the diaphram seals. It was just large enough to keep the valve open once it was opened by the solenoid but when I closed the downstream mechanical valve the flow was stopped and the diaphram would reseal. Any larger and the valve would never seal and any smaller it would have gone unnoticed. Obviously Rainbird gave me bad info because the valve works just fine now. Thanks again for the suggestions.


Rays Sprinklers

Supreme Member

Posts: 493

Location: USA

10

Sunday, July 27th 2003, 11:30am

Glad everything works!

Thanks
Ray
Rays Above and Beyond Automatic Lawn Sprinklers
Thanks
Ray
Rays Above and Beyond Automatic Lawn Sprinklers

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