Pressure range for well pump and water hammer questions

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msoultan

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I'm helping a friend with his well setup and I wanted to get some advise. There's a submersible pump in the well which then leads to a check valve, then a T fitting for the pressure switch and another T for the pressure tank - unfortunately I don't have any details on the pump model or its depth. From there the pipe travels up to a 5000 gallon storage tank and there's a float valve to shut off the water which in-turn causes the pressure to rise and trigger the pressure switch by the pump. There is another pump that then pumps the water to the house, so the submersible pump is only pumping water from the well to the storage tank and not providing water directly to the home. Unfortunately I don't know how many feet of water head I have between the tank and the pressure switch because someone installed the pressure gauge on the pump side of the check valve instead of next to the pressure switch, so I will be fixing that tomorrow so then I can have an accurate measurement. It seems to be about 30ft of elevation gain and about a 100ft run of 1" pipe. When the pump is running, the pressure reading is 15 PSI and I'd venture to guess it's somewhere around 5-10 GPM of flow based on looking at it - I have yet to verify that.

We just changed out an old Square D pressure switch (which is labeled as a 20/40) because it stopped working (contacts were shot), but based on how the recently installed pressure tank was configured (38 PSI), I was skeptical that the switch was actually set for 20/40 because that's how the tank should be configured for 40/60 pressure switch (I'm guessing they just left the tank at the factory-set pressure). So I made up a fixture and tested the switch and it is configured for 33/55, so I'm guessing that someone bumped up the range, and the 2 PSI difference is probably within the error of an old switch (i.e. I doubt they changed the differential significantly). Either way, the recent service to have the tank installed wasn't done correctly.

When I first installed the new switch (configured for 20/40), it would get into an on/off oscillation when the float was raised/lowered too fast, so I'm guessing we're running into a water hammer issue, so for the time-being I raised the pressure cutoffs to 30/50 which alleviated that (with the incorrectly configured pressure tank), but it's only until the float valve really closes that the pressure starts to slowly climb until it reaches 50 PSI. If you leave the float valve closed, the pump can reach 70 PSI after a while, but it seems like it's working hard above 40 PSI to reach that point.

So, it seems like there are a few issues - there's a potential water hammer issue, the pressure switch is set higher than it needs to be, and the pressure tank is not configured correctly. Here's what I was thinking - what if I set the pressure switch down to 20/40, drop the pressure tank to 18 PSI, and then put a check valve just after (downstream) of the pressure switch to stop the oscillations from reaching the pressure switch - does this sound like a feasible solution? Or, if I were to drop the pressure tank down to it's correct cutin pressure-2 PSI value, would that alone alleviate the oscillations affecting the pressure switch and avoid the need for another check valve after the pressure switch?

One other thing - should float valves require a lot of upward force to stop the water flow at 50 PSI (or even 30 PSI), and/or does that required amount of upward force decrease when the system is at a lower PSI? I noticed that it took a good amount of upwards force for the float to finally shut off the water. In other words, does the upward force required to close a check valve increase with the PSI in the pipe it's closing off, or does it sound like the valve probably needs to be replaced? What was happening is that pressure would build, shut off the pump, but water was still coming out of the float valve (slowly) and eventually the pump would kick back on, build up pressure, and it would eventually shut off again.... just seemed a little strange. A properly adjusted pressure tank here would probably help with runtimes regardless, but I was curious as to whether those float valves are meant to shut off at a set deflection, regardless of system PSI.

Thanks!!
 

Valveman

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A "properly" sized pressure tank and increased run time will not help save the pump from cycling itself to death. The fill valve to the cistern needs to be able to let out enough water to keep the pump from cycling on/off, as when filling a cistern the pump won't last long if allowed to cycle like that. A non-modulating float valve is needed that maintains a set flow rate until the float valve closes. A regular float valve will modulate and vary the flow filling the cistern, causing the well pump to cycle on and off. My favorite is an electric solenoid valve like used for sprinklers. With a flow control knob the flow rate can be adjusted as needed and there is no modulating. it is either full open or fully closed.

wiring diagram for 24v solenoid, plug in trans, and float.png
 

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The water hammer is being caused by the check valve at the tank. There should be no other check valves in the system except for the one down on the submersible pump. Remove the check or you can just gut it so it doesn't work for anything other than a place to install the pressure switch.

A Cycle Stop Valve on the well pump would allow for the float valve to vary the flow rate some. But when the flow rate becomes less than 1 GPM, even the CSV will let the pump cycle on and off. it is best to not have a modulating fill valve.

Cistern Storage Tank with JET Booster Pump (12).png
 

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Oh and BTW, all you really had to say was that there is water hammer on pump start, and the pressure switch points keep burning out on the pump that feeds a cistern. That is the first sign of too much cycling and tells me everything I need to know about the system. :)
 

msoultan

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Thanks for all the info! So there is no check valve at the tank - the only check valve is directly after the pump, before the pressure switch, so I think the water hammer is just from us closing the float valve at the tank by hand too quickly (which really wouldn't happen in real-world scenarios). I would guess that adding a check valve just after the pressure switch would alleviate the switch cycling due to hammer, but I think that's just a band-aid fix for the reason you mentioned where it's still going to cause the pump to cycle way more than it needs to.

I took another look at the system today and what I noticed is that there are currently two float switches in the tank - one is a low-level switch that keeps the house pump from running empty, but there's also a high-level switch that currently isn't connected to anything! It looks like it might have been used to control the well pump a while back, but the wire running back to the pump doesn't seem to be functional any more. So, I'm going to employ the solution you suggested with the solenoid valve installed in the fill pipe and then utilize the float switch that's already in there - there's already a 120v outlet next to the house pump so that's easy. The pressure switch has been replaced, configured for 20/40, pressure tank set to 18 PSI (even though it really isn't needed, but it's already there), so at least that part of the system is working.

I think the ideal setup is to have the float switch drive a contactor and eliminate the pressure switch entirely, but then I'd have to run wire from the tank to the pump, which wouldn't be the end of the word, especially if it were low-voltage. But I think the suggestion you provided will work nicely.

I'm looking at the following:


Seems like that should do the trick.

Thanks for your help!!
 

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If you are going to run wires from the float switch the picture in post #3 shows how to do that. You may not even need a relay if the float switch is rated for enough amps to run the pump.

Using the pressure tank and pressure switch for the well pump, the solenoid valve way is shown here.
Cistern Storage Tank with Submersible Booster Pump 2 Homes.png
 

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Usually a float switch doesn't have much of a level differential might only be a inch or two causing short cycling. One with n.o. contacts the other n.c. Line voltage contactor. Could use the existing low level float for a safety low level. Floats seem to work better if there mounted in a pipe so the water is calmer.
 

Reach4

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I'm helping a friend with his well setup and I wanted to get some advise. There's a submersible pump in the well which then leads to a check valve, then a T fitting for the pressure switch and another T for the pressure tank - unfortunately I don't have any details on the pump model or its depth. From there the pipe travels up to a 5000 gallon storage tank and there's a float valve to shut off the water which in-turn causes the pressure to rise and trigger the pressure switch by the pump.
There are moderatingmodulating float valve, which close partially depending on the float position, and non-moderating float valves that snap closed.
 
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msoultan

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If you are going to run wires from the float switch the picture in post #3 shows how to do that. You may not even need a relay if the float switch is rated for enough amps to run the pump.

Using the pressure tank and pressure switch for the well pump, the solenoid valve way is shown here.
I was considering having the float switch directly control the pump (it's a common SJE Rhombus grey float switch with the weight), but then I'd have to run conduit and it's a long run (over 100ft) - would be much easier and safer to run a 24v control line and trigger a contactor instead. But I'm gonna go with your suggestion from post #2 as it's a good solution without having to change much in the system, especially because there's already a float switch installed and ready to go. I manage a water distribution system that uses pretty much the exact same setup you suggested (except their water comes from the city) and that works pretty well, so I'm all for using a proven method :)
 

msoultan

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Usually a float switch doesn't have much of a level differential might only be a inch or two causing short cycling. One with n.o. contacts the other n.c. Line voltage contactor. Could use the existing low level float for a safety low level. Floats seem to work better if there mounted in a pipe so the water is calmer.
The float switch that was previously used in the tank at the high level location is a normally closed SJE Rhombus float switch - looks like it was previously used to control the pump, at least that's what I'm guessing because there some NM wire running over to the pump station. So I'm guessing at one point they were using the switch to directly trigger the pump. That being said, the NM wire isn't run properly, doesn't seem to have continuity, and the conduit is filled with water, so there's no way I'm going to trust that existing system. The solution that Valveman provided in post #2 seems like a simple solution that also allows me to utilize existing hardware. And maybe at some point, if we were really inclined, I could run a 24v control signal with a contactor at the pump station and eliminate the pressure switch entirely, but I don't think we really need to go that far as the pressure switch is working nicely since I've replaced it.
 

msoultan

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There are moderating float valve, which close partially depending on the float position, and non-moderating float valves that snap closed.
I would be curious about this solution - do you happen to have a product that you'd recommend? This is the current valve that we have:

 

Fitter30

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Where a solenoid valve slams shut a motorised ball valve takes a few seconds to open & close. Domestic water.
 
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msoultan

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Where a solenoid valve slams shut a motorised ball valve takes a few seconds to open & close. Domestic water.
So the solenoid valve I found is a slow close to avoid water hammer. I specifically made sure to find one that didn't slam shut.
 

msoultan

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Something like this is non-modulating and is either fully open or fully closed.
That is awesome! How do you like them and are they reliable? They aren't cheap, but it's either my time or a nice valve that accomplishes the same thing, and less failure points than adding a solenoid valve. So, given the choice, would you go with this or adding a solenoid? I'm kinda leaning towards this because then I just need to remove the existing float valve instead of adding the solenoid valve, 24v transformer, etc. The solenoid valve is an easy update as well, but this looks like it could be easier with less points of failure (assuming it's a reliable device).
 

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Only know of Jobe valves from some of my customers. I like the solenoid with flow control knob. With either type valve it is important they put out enough water to keep the pump from cycling off but not so much that the pressure at the pressure tank falls to zero. A Cycle Stop Valve on the well pump will adjust to any rate filling the cistern. But without a CSV the float/solenoid valve must be adjusted accordingly to prevent cycling. Also, with the flow control knob set for a reduced flow rate the valve is not all the way open and it closes much more gently, no hammer.
 

msoultan

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Only know of Jobe valves from some of my customers. I like the solenoid with flow control knob. With either type valve it is important they put out enough water to keep the pump from cycling off but not so much that the pressure at the pressure tank falls to zero. A Cycle Stop Valve on the well pump will adjust to any rate filling the cistern. But without a CSV the float/solenoid valve must be adjusted accordingly to prevent cycling. Also, with the flow control knob set for a reduced flow rate the valve is not all the way open and it closes much more gently, no hammer.

In my case I have 15 PSI at the pressure switch (so it's not 0), but why would you need some kind of back pressure to avoid cycling? Or are you saying it can't be so restrictive that it causes the PSI to jump up to 40? In my case the pressure switch is set for 20/40 so anything below 40 will keep the pump on anyways - am I missing something? Not understanding why the pressure dropping to 0 will cause the pump to cycle.

Just FYI, the solenoid valve I linked to in post #5 performs a slow close.
 

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Now that I look, I don't find reasonably priced modulating float valves. You could put a big water hammer arrestor or small pressure tank on the upstream side of a fast valve to absorb the water hammer shock.
 

msoultan

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Now that I look, I don't find reasonably priced modulating float valves. You could put a big water hammer arrestor or small pressure tank on the upstream side of a fast valve to absorb the water hammer shock.
I've spent the past hour or so looking at all sorts of diaphragm float valves and the decision is either Jobe (originally linked above) or Apex (which is also Watts). The Apex is about $80 where the Jobe is around $280. Both of these units are soft-close, but we do have a pressure tank next to the well, so it's double protected from water hammer. I don't know why there's such a big disparity in pricing between the two. The nice part about the PumpBuddy is that there isn't a float sliding up and down to wear out the string - but maybe that's what makes the Jobe better? I'm gonna send Jobe an email to find out why they're so much more expensive and see how they justify it.

Apex PumpBuddy

Jobe Topaz Differential:

There's also this one for $56 on Amazon, but I'm not sure I trust it:
 

Reach4

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The nice part about the PumpBuddy is that there isn't a float sliding up and down to wear out the string - but maybe that's what makes the Jobe better? I'm gonna send Jobe an email to find out why they're so much more expensive and see how they justify it.
You could instead send an email to PumpBuddy, and ask if they are NSF 372 Certified for potable water systems, and why not.
 
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