Author Topic: Concern with higher pressure between pump and CSV  (Read 888 times)

cpufrost

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Concern with higher pressure between pump and CSV
« on: June 23, 2019, 07:12:30 PM »
I just replaced my pump which was only 5 years old.  The pump wasn't bad but was detached due to starting torque.  (unthreaded)  Rather than drop the 5 year old pump back down a 150' hole I opted for a new one as luck has it I don't want to be pulling it in two feet of snow!

Anyhow, the pump is a 3/4 hp two wire and the well is about 100' from the house.  It's connected with HDPE tubing (150PSIG cold working) 1" ID via a standard pitless adapter. 

I do NOT have a check valve on the tank manifold (Amtrol 20 gallon) but I have a Harvard 1 1/4" Stainless Steel high quality spring check threaded right into the pump which has its own check valve.

The system works fine and produces plenty of water.  The cut in is 55 and cut out 75.  It's higher than the standard 40/60 because I have an RO/DI 200gpd watermaker for several things I need pure water for.  I want a steady 60-65 psig to the house.  Sounds simple enough.

My question is, with a 1gpm flow through, understandably your valve is essentially restricting the pump output so the pressure BEHIND the valve down to the pump outlet is going to be MUCH higher and that's worrisome.  I don't want a leak to develop!  And the thought of replacing the line with 1" SCH80 PVC is "it's not happening".

Should I be concerned?

Thanks in advance.

Cary Austin

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Re: Concern with higher pressure between pump and CSV
« Reply #1 on: June 24, 2019, 06:53:32 AM »
Back pressure is something we check when sizing a CSV, but it is rarely enough to be a problem.  A 3/4HP, 10 GPM pump can only produce 134 PSI total.  This steady back pressure is far easier on the pipe than the water hammer that happens when a pump without a CSV starts and stops.  Water hammer can cause pressure spikes five times higher than the pump can even build.  Also the burst pressure of pipe is 2 to 5 times higher than the rated pressure.

cpufrost

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Re: Concern with higher pressure between pump and CSV
« Reply #2 on: June 24, 2019, 06:13:18 PM »
That makes sense, and yes I'd say water hammer can be scary bad when there's a check valve at the tank and there's a leak near the pump!  Literally sounds like someone hitting the floor joists with a sledgehammer!  Dynamic pressure easily 10X higher.  Makes me shudder to think that some installers use plastic barbs.