Author Topic: CSV1A and low flow rate  (Read 894 times)

Kent M

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CSV1A and low flow rate
« on: July 23, 2022, 08:57:13 PM »
I've had a CSV1A installed for ~ 7 years and it's been great!  It replaced the CU301 controller and pressure transducer on our 18 year old Grundfos SQE pump, turning it into an SQ pump I guess.

At the 80' pumping depth on our 130' well, that pump has been able to supply over 20 gpm at whatever pressure was asked of it...until lately.  Now if a couple sprinklers are running concurrently, the flow rate is noticeably lower than in years past and the pump is unable to maintain the pressure set on the CSV1A.  If I hook a hose up to the 3/4" spigot near the pressure tank and turn it on full, the pressure will drop enough to empty the tank and kick off the Square D M4 pressure switch.

I disassembled the CSV1A a couple days ago and it looked fine - no holes in the diaphragm, no sand packed into any of the openings, just a little iron staining that wiped off easily. It has no trouble maintaining a pressure for a low flow like a shower or two, just at higher flow rates.

Is there any type of failure in a CSV1A that would cause these symptoms?  My guess is it is not the valve, but would like to be sure before calling in the well servicing company.  Would it be possible to temporarily remove the guts of the valve and replace it with an o-ring and flat disk of sheet metal that the pressure adjusting spring and cage would hold in place?
« Last Edit: July 24, 2022, 03:50:50 PM by Kent M »

Cary Austin

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Re: CSV1A and low flow rate
« Reply #1 on: July 24, 2022, 05:05:31 PM »
Just tightening the bolt down 2-3 rounds will completely disable the CSV if you want to test it.  But the CSV is not the problem or I would have already waved my magic wand around and fixed it for you.  Lol!  Sounds like the pump is wearing down.  Those SQ and SQE pumps spin 10,700 RPM instead of 3,450 like regular pumps.  I have always been afraid they would wear much quicker as doubling the speed quadruples the wear rate.  They have composite impellers that are probably worn down.  Check the amps at mx flow rate, as I bet the amps do not max out, meaning the pump is worn.  I would like to know if this is the case. Please keep the pump and if yo don't tear it down send it to me for an autopsy.  Thanks.  Cary

Kent M

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Re: CSV1A and low flow rate
« Reply #2 on: July 24, 2022, 08:57:53 PM »
Thanks for the quick reply, Cary!  The well does produce some fine sand - the 100 micron flush-able filter catches an ounce or so in a couple months, so it's likely the impellers are wearing down.  I'll run those tests you suggested this week.

Any recommended 4" pump brands/models to look for if the Grundfos is worn out? 

Cary Austin

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Re: CSV1A and low flow rate
« Reply #3 on: July 25, 2022, 10:17:19 AM »
The Grundfos SQ is a good 3" pump.  But the 10,700 RPM and composite impeller might not take sand as well as the 3,450 RPM used in 4" pump.  Grundfos also makes very good 4" pumps and they have similar sizes and model numbers to the 3" SQ.  Which SQ did you have?  Also, I would like to see the hub on those impellers, just out of curiosity. 

Kent M

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Re: CSV1A and low flow rate
« Reply #4 on: July 25, 2022, 08:20:29 PM »
The pump is a 15SQE-250 1HP.  I measured the amperage today while it was running at max - 7.8 amps.  The literature from Grundfos says 7.6 amps max for that pump, so it's pretty close.

I noticed that the adjusting bolt on the CSV1A was feeling rather rough while turning, so I disassembled it again and found that the bolt was damaged.  After replacing it with another 3/8-16 bolt and new nuts, it still doesn't feel "right".  Should the diaphragm assembly be movable by hand when the top bolt (on the assembly, not the adjusting bolt) is tight?  I can only get any movement of the white valve body by hand when the bolt is loosened.
« Last Edit: July 25, 2022, 08:38:22 PM by Kent M »

Cary Austin

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Re: CSV1A and low flow rate
« Reply #5 on: July 26, 2022, 06:49:33 AM »
The bolt and spring keep the white gut pack pushed open.  So, no you shouldn't be able to move it until you loosen the bolt.  7.6 amps means the pump is producing max flow.  Maybe the pumping level is deeper than before, there is a hole in the drop pipe, or a filter is clogged.

Kent M

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Re: CSV1A and low flow rate
« Reply #6 on: July 26, 2022, 11:48:13 AM »
There is something wrong with the CSV1A valve.  This morning I took it apart, put only the diaphragm and a flat sheet metal disk on top of it and reassembled.  The pump is pushing 12-14 gpm out the tank drain spigot through a 3/4" 50' garden hose, while holding 64 psi!  It's like a mini-fire hose!

So, good news that it's not the pump, plumbing or valve housing.  I've attached some pictures of the valve body, in case you can spot a problem.  It seems to me that the 1/8" gap isn't sufficient to pass up to 25 gpm, but I couldn't get it to open any more than that.

Cary Austin

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Re: CSV1A and low flow rate
« Reply #7 on: July 26, 2022, 12:36:43 PM »
Yes that is all it opens for 25 GPM flow.  Pretty simple valve, and doesn't look like anything is wrong with it.  Your pump is just not building as much pressure as it once did.  If it is only building 64 PSI without the CSV, then it will have about 10-15 PSI less than that with the CSV installed.  For the CSV1A to work properly the pump needs to provide 10-15 PSI more than the system pressure required.  I could send you a new gut pack, but it won't change anything.  That valve is designed to always give a little restriction.  Your pump just wore down until it has no cushion left.

Our CSV125 and CSV3A2T have much less friction loss when working with a pump that has no cushion. 


Kent M

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Re: CSV1A and low flow rate
« Reply #8 on: July 26, 2022, 08:45:22 PM »
Ok, good info, thanks, Cary!  I'll probably leave it bypassed/gutted for now and see how it does.  It still reaches the switch cutoff of 74 psi easily with normal demand flow, but I might look for a local pump repair business that could rebuild the wet end of the pump at some point.  It will be easy enough to put the CSV1A back into service then.