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Old 07-29-2013, 08:17 PM
sprinklrz sprinklrz is offline
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Velocity/Pressure Causing Valve to Stay Open?

If you have a 2 1/2 inch mainline with a sudden drop down to a 1 1/2 inch valve then immediately back up to a 2 1/2 inch pipe, wouldn't you still have a massive increase in velocity through those smaller pipes and valves?

Could the increase in velocity be enough to keep a valve from closing?

There is a booster pump involved too which boosts the pressure way up. I can't remember for sure off hand the working pressure of this booster pump but it's up there.

Is there a possibility that high pressure alone can keep a valve from closing?

Thanks.
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Old 07-29-2013, 09:01 PM
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Wet_Boots Wet_Boots is online now
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It is very common design practice to have an electric diaphragm valve sized smaller than the pipe it's connected to. In other words, find another reason for the valve sticking open.
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Old 07-29-2013, 09:06 PM
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Quote:
Originally Posted by Wet_Boots View Post
It is very common design practice to have an electric diaphragm valve sized smaller than the pipe it's connected to. In other words, find another reason for the valve sticking open.
Yea, and even mainline sized larger than water supply.
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Old 07-29-2013, 09:13 PM
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Quote:
Originally Posted by sprinklrz View Post
If you have a 2 1/2 inch mainline with a sudden drop down to a 1 1/2 inch valve then immediately back up to a 2 1/2 inch pipe, wouldn't you still have a massive increase in velocity through those smaller pipes and valves?
Depends on your demand. If you have a demand of 3 gpm then the answer is no. If your demand is 150 gpm then your answer is maybe so.
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Old 07-29-2013, 09:54 PM
sprinklrz sprinklrz is offline
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It's been giving me fits. It's not just one valve, apparently, seems to be more than one. It seems to be that possibly the valves don't close until the booster pump is overwhelmed and shuts down. The load is not very great, just a few Hunter MP Rotators per zone. Got plenty, plenty of water available.
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Old 07-29-2013, 10:08 PM
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Originally Posted by sprinklrz View Post
just a few Hunter MP Rotators per zone. .
And you have a 2 1/2 inch mainline?
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Old 07-29-2013, 10:28 PM
sprinklrz sprinklrz is offline
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Actually, a 4" main fed from 2-2" backflows/meters to the booster pump.
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Old 07-29-2013, 10:57 PM
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Originally Posted by sprinklrz View Post
Actually, a 4" main fed from 2-2" backflows/meters to the booster pump.
http://www.lawnsite.com/showthread.php?t=409246
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Old 07-30-2013, 01:02 AM
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You haven't mentioned brand name of valves so i can only generalize.

The valves can prolly handle 120 gpm and 150 psi.

The 2.5 pipe can handle 70 gpm and be under 5 fps.

Determine the demand on each valve. Compare the working vs the non-working valves. There will be a pattern or a break in a pattern that you should see.

Measure the static AND dynamic pressures of the system. You may find that the pressure isn't what you think it is.

As always i suggest that you measure the resistance - voltage - amperage of each valve at the clock first to eliminate electrical issues.

Bring back some solid numbers and someone may see something that you're not seeing. Best of luck
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Old 07-31-2013, 02:36 AM
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Quote:
Originally Posted by sprinklrz View Post
It's been giving me fits. It's not just one valve, apparently, seems to be more than one. It seems to be that possibly the valves don't close until the booster pump is overwhelmed and shuts down. The load is not very great, just a few Hunter MP Rotators per zone. Got plenty, plenty of water available.
Maybe your valve is oversized. If the valve is clear of debris, have you tried turning the flow control in?
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