Centrifugal pump loses prime overnight.

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Old 09-10-19, 08:34 AM
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Centrifugal pump loses prime overnight.

I have a Sta Rite 3hp self-priming centrifugal pump drawing from a river for irrigation. Recently it started losing prime between uses. I’ve checked the suction side for leaks and found nothing. I’ve also checked the pressure side with similar results. I’ve replaced the check valve and I’ve opened up the suction line and verified that the check valve is holding. The pump shows no sign of leaking anywhere, especially around the shaft seal. Any suggestions for what I’m missing? I’ve inspected the pickup and it is clear. Once the pump is primed it runs normally and produces normal pressure and volume. I’m stumped and could use some help.
 

Last edited by Cyberay; 09-10-19 at 08:47 AM. Reason: Added information.
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Old 09-10-19, 12:07 PM
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Welcome to the forums.

The sole purpose of the check valve is to keep the line full of water for faster priming.
If you are losing the prime.... the check valve is not holding.
 
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Old 09-10-19, 12:17 PM
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If your suction line is full of water you have a pump problem.
 
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Old 09-11-19, 09:34 AM
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Problem found. Suction line separating underwater ahead of the check valves was the cause of the problem. Thanks for your replies.
 
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