Author Topic: Concerned about potential max pressure on pump side of CSV  (Read 388 times)

bytenik

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Concerned about potential max pressure on pump side of CSV
« on: March 30, 2020, 07:44:12 PM »
Hello,

I have a Goulds 5GS10 (1 HP) well pump. I'm looking to put a CSV1A into my system to deliver constant pressure. However, I have a concern. The CSV1A kicks in at a minimum of 1 GPM according to the literature I've read. At 1 GPM, this pump's curve claims it builds about 650 ft of head. The static water level in the well is about 100 ft. I'm not sure what the pressure rating of the drop pipe to the well pump is, but, the delivery pipe would get 550 ft of remaining head. Wouldn't that apply around 240 PSI to the delivery pipe? Its a 1" SIDR9 HDPE line rated at 200 PSI, 40 PSI lower than the maximum build pressure of the pump. Isn't there a concern about bursting? I was also planning on using Uponor PEX with ProPEX fittings between the check valve and the CSV inside the house, but Uponor rates their PEX as up to 150 PSI. I've got the same concern there.

I know 1 GPM is an unrealistically low flow rate for nearly everything in a residential home, but, I'm just trying to plan for a worst-case scenario -- perhaps a sink that's been turned on to just the right amount of flow, etc.

I feel like I must be missing something because plenty of people seem to use the CSV1A with a 1 HP pump successfully, and I doubt you'd have happy customers if everyone's delivery pipe and/or interior plumbing before the CSV was blowing up. ;D What am I missing?

Cary Austin

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Re: Concerned about potential max pressure on pump side of CSV
« Reply #1 on: March 31, 2020, 07:05:36 AM »
Your problem is you have a pump designed for 600 plus feet of lift and it is only 100' to water.  A 10 GPM, 1HP would be a much better pump as long as the water level doesn't get deeper than about 200'.  Back pressure is a concern in situations like this, and is something we always check when using a CSV.  Yes with the 5GS10 and static at 100' there will be 290 PSI on the pipe which is too much.  With a 10 GPM pump end on that 1HP motor the back pressure before the CSV would only be 121 PSI and the pressure on the bottom section of pipe would only be 164 PSI. 

A water level of 100' is not even deep enough to keep a 5GS10 pump from upthrusting.  Wrong pump for such a shallow water level and it builds more pressure than the pipe and CSV can handle.  Sorry.  If you ever replace the pump with one more suited for that depth a CSV would then be a good option.

bytenik

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Re: Concerned about potential max pressure on pump side of CSV
« Reply #2 on: March 31, 2020, 04:04:40 PM »
Unfortunately, we're somewhat stuck on the type of well pump. The water level changes pretty dramatically seasonally. We'll be at 120 ft and then six months later we'll be at 500 ft. The aquifer behaves very oddly. This apparently happens to our neighbors too, to the point where they drilled an additional few hundred feet to 825. The well is drilled 650 ft deep. It also produces very slowly, so after a bunch of use the water level drops dramatically as well. The pump is set at 575 ft. It is unfortunate that I have to do everything for worst-case scenarios, which for the CSV means 1 GPM and 100 ft of water, and for the pump I need to size for 500 ft deep water.

Cary Austin

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Re: Concerned about potential max pressure on pump side of CSV
« Reply #3 on: April 01, 2020, 07:01:03 AM »
You might consider using a cistern storage tank and a booster pump.  The storage tank will store water in times where the well is not supplying much water.  The booster pump could use a CSV to deliver as much water at a strong constant pressure to the house.  Supply and pressure would be much better this way  and it takes a lot of wear and tear off the hard to replace well pump.

bytenik

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Re: Concerned about potential max pressure on pump side of CSV
« Reply #4 on: April 01, 2020, 08:11:34 AM »
Wouldn't I have the same problem though with the pump filling the cistern? Either I'd have to run the pump at "full tilt," with no flow restriction, at which point the well would run dry because the pump can do more GPM than the well can restore, or, I'd have to put in a flow restriction to limit it to 2-3 GPM, at which point I'd have the same build up of pressure on the line.

Cary Austin

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Re: Concerned about potential max pressure on pump side of CSV
« Reply #5 on: April 01, 2020, 08:43:05 AM »
Correct you would not be able to restrict the flow from the well pump without causing high pressure in the water line.  But if the pump will run for at least a minute or two at full tilt you don't need to restrict the flow.  Just use a Cycle Sensor that knows when the pump is running dry and shuts the pump off.  The Cycle Sensor has a built in restart timer.  After the pump is shut off from running dry, the Cycle Sensor can be set to restart the pump from 1 minute to 5 hours later.  Just let the well recover long enough for the pump to run at least a minute at full tilt when it comes on.  If it won't run for a minute you can restrict that pump to 5 GPM or so and not build more pressure than the pipe can take.  I can look up the pump curve and tell you the minimum you can run if you would like?

bytenik

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Re: Concerned about potential max pressure on pump side of CSV
« Reply #6 on: April 01, 2020, 09:53:42 AM »
Hmm, that's interesting. It certainly should run for over a minute. Is it safe to run the well dry repeatedly? I had heard from the driller who replaced the
pump for us 5 years ago that it can cause sediment kickup and other issues that I don't recall.

Would it make sense to add a flow restriction and also a pressure bypass valve (maybe a Poppet or something) so that the well pump would not be able to build over a certain pressure. Below that pressure, it would flow through the flow restriction, and above it, it would flow through the bypass. I would guess this would mean that it would run through the bypass until the water level dropped in the well to a certain height, and after that it would run through the restricted pipe. I'm not sure what the lifespan of a Poppet valve is though and if it could go through repeated cycles. I know they're usually used as a pressure relief to atmosphere.

Come to think of it, would a similar set up work to bypass the CSV if I didn't do a cistern? If the worst case situation of low flow and high water occurred, it would bypass and I would be left with the existing behavior of the well (cycle on/off as the pressure tank fills/drains), and when the water is lower and/or the flow is higher such that the pressure doesn't build above a safe number, water would flow through the CSV. I'm mostly interested in constant pressure for things like showers, etc, which are 3 GPM+ shower heads in my house, and its fairly rare for the water level to be at 100 ft. I just checked it before posting now (I have an Enoscientific Well Sounder) and its at 240 ft currently. I would still use HDPE for all piping prior to the CSV inside instead of PEX to avoid the 150 PSI rating that Uponor gives their PEX -- I'm sure I can find a supplier with SIDR7 (250 PSI) sticks of pipe or something like that to use.

What are your thoughts on both of the options I proposed (bypass into cistern, and/or bypass across CSV) and both compared to just using a Cycle Sensor. (BTW, I do already have a Cycle Sensor, because I ran into enough instances of running the well dry and I was concerned with damaging the pump. Its a great product! So with any of these options I still would have a Cycle Sensor in there to protect the pump "just in case.")

Cary Austin

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Re: Concerned about potential max pressure on pump side of CSV
« Reply #7 on: April 01, 2020, 11:09:16 AM »
Ok I did the math on that pump.  As long as you are pumping at least 5.5 GPM there cannot be more than 200 PSI on your pipe.  When pumping directly into a cistern if the water level is less than 250' that pump wants to produce 7-8 GPM.  The best you can do is a 6 GPM Dole valve.  Dole valves have a rubber disc that expands into the 6 GPM orifice when the pressure is high and retracts when the pressure is low.  This helps the Dole valve self regulate the 6 GPM regardless of the water level in the well.  Then you don't need the complication of the bypass you are thinking of. 

Using the Cycle Sensor most wells can be pumped down repeatedly many times before the float switch hits the full level in the cistern.  If the sediment gets stirred up when the water level drops to the pump, you can set the amperage on the Cycle Sensor to shut the pump off before the well pumps dry.  As the water level in the well drops the amps on the Cycle Sensor will drop and you can set the Under Current cut off to shut the pump off at a certain water level if needed.