Well pump help

[Valveman]

Good idea. Here are the numbers: 19 GPM produces a pressure of 38 PSI which is equivalent to 87'. Graph shows TDH for 19 GPM is 260'. This leaves 173' for depth to water + friction. At the other extreme, 44 PSI at zero flow (330' TDH) leaves 229'. Not very similar. Also hard to explain failure to reach 60 PSI at zero flow unless it really takes a long time (half hour?)

380' of 1" pipe would have about 25' friction loss, which would make the pumping level 148'. 1 1/4" pipe would have about 13' loss, which would make the pumping level 160'. Worst case of the water level being 160' would mean your pump can build 73 PSI at the surface. And yes it would take a long time to fill a tank to 60, because the differential pressure through the CSV is only 13 PSI. So you would be filling the tank at about 1/10th of a GPM. The closer it gets to 73 the less differential pressure there is and the lower the flow through the CSV. So you really can't do a deadhead pressure test through a CSV to check the water level that way.

But worst case of 160' pumping level that pump will produce 18 GPM at 50 PSI. All you really need to do is move that CSV12550-1 closer to the surface so it is actually working at 50 PSI. Then set the pressure switch to shut the pump off at about 54 PSI. Or again you can use a CSV12560-1 if you want to set it back 20' below ground as you are now.

 

[Reach4]

http://www.engineeringtoolbox.com/hazen-williams-water-d_797.html is a pipe calculator. I plugged in 500 ft of 1 inch pipe carrying 1 GPM of water. It calculated 0.2 PSI pressure drop.

 

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[Leeelson]

380' of 1" pipe would have about 25' friction loss, which would make the pumping level 148'. 1 1/4" pipe would have about 13' loss, which would make the pumping level 160'. Worst case of the water level being 160' would mean your pump can build 73 PSI at the surface. And yes it would take a long time to fill a tank to 60, because the differential pressure through the CSV is only 13 PSI. So you would be filling the tank at about 1/10th of a GPM. The closer it gets to 73 the less differential pressure there is and the lower the flow through the CSV. So you really can't do a deadhead pressure test through a CSV to check the water level that way.

But worst case of 160' pumping level that pump will produce 18 GPM at 50 PSI. All you really need to do is move that CSV12550-1 closer to the surface so it is actually working at 50 PSI. Then set the pressure switch to shut the pump off at about 54 PSI. Or again you can use a CSV12560-1 if you want to set it back 20' below ground as you are now.

I don't see how I can get 54 PSI (in a reasonable amount of time) at the surface by moving the CSV. The problem is the low pressure differential, as you point out. So, assuming I replaced the CSV with a 12560-1, my pressure operating range would be, at best, 30-50 PSI. As was pointed out to me, that leaves no margin for error so if the water level dropped 20 feet in summer (or in 5 years), unless I monitored and adjusted the pressure switch, I run the risk of burning out the motor. Not much margin for error.

 

[Reach4]

As was pointed out to me, that leaves no margin for error so if the water level dropped 20 feet in summer (or in 5 years), unless I monitored and adjusted the pressure switch, I run the risk of burning out the motor.

No. Yes, your GPM would drop. The motor would not burn out, because there would be enough flow to cool the motor. At 2 GPM, the dynamic loss would be under 2 PSI.

 

[Leeelson]

No. Yes, your GPM would drop. The motor would not burn out, because there would be enough flow to cool the motor. At 2 GPM, the dynamic loss would be under 2 PSI.

Except that as was pointed out by valveman, the flow goes down to 1/10 GPM

 

[Leeelson]

This just in. Dead head pressure with CSV removed is 100 PSI. The CSV has quite a large effect. I wonder if a more powerful pump (150 PSI) would change the pressure much with the CSV installed.

 

[Valveman]

This just in. Dead head pressure with CSV removed is 100 PSI. The CSV has quite a large effect. I wonder if a more powerful pump (150 PSI) would change the pressure much with the CSV installed.

Of course the CSV has a large effect. Because of where it is installed it is a 40 PSI CSV. So it wants you to have 40 PSI no matter how much or how little water you are using. With 100 PSI deadhead from the pump your water level should be at about 100'. And with 100 PSI deadhead and a pressure switch off setting of 60 PSI, that is a 40 PSI differential across the CSV. 40 PSI differential makes the minimum flow through the CSV about 1/2 of a GPM. This is plenty to keep the pump/motor cool, especially since it is a good pump and the amps drop from 10 to 4. At 4 amps the motor doesn't need much cooling so 1/2 GPM is more than adequate. And the 1/2 GPM is the rate that will fill the pressure tank after all the faucets are closed.

So with the CSV12550-1 installed 20' below the surface you still need a pressure switch setting of about 24/44, and the CSV will provide 40 PSI constant while you are using water. With the CSV set just below the surface it would deliver 50 PSI constant while you are using water and would need a pressure switch setting of about 34/54.

I hope since you know the deadhead pressure with the CSV removed that you did not let an uneducated installer tell you the CSV was no good and just take it out of service? The CSV is a very simple valve and therefore doesn't cause any problems. When there are problems it is always because of something else, but the CSV usually gets the blame as the installer just doesn't know what he is doing. It is not that complicated and we are always here to help. But we can't do anything to help when the installer just takes it on himself to decide to put the CSV 20' deeper than it should be, just because he doesn't understand how it works and setting it 20' deeper is easier than cutting and threading a piece of pipe.

Your pump can build 100 PSI. So without the CSV it can easily reach 60 PSI even while you are using water. This will cause the pump to cycle on and off repeatedly while you are using water and have all the problems that go with cycling instead of just running steady as it will with the CSV.

 

[Leeelson]

Of course the CSV has a large effect. Because of where it is installed it is a 40 PSI CSV. So it wants you to have 40 PSI no matter how much or how little water you are using. With 100 PSI deadhead from the pump your water level should be at about 100'. And with 100 PSI deadhead and a pressure switch off setting of 60 PSI, that is a 40 PSI differential across the CSV. 40 PSI differential makes the minimum flow through the CSV about 1/2 of a GPM. This is plenty to keep the pump/motor cool, especially since it is a good pump and the amps drop from 10 to 4. At 4 amps the motor doesn't need much cooling so 1/2 GPM is more than adequate. And the 1/2 GPM is the rate that will fill the pressure tank after all the faucets are closed.

So with the CSV12550-1 installed 20' below the surface you still need a pressure switch setting of about 24/44, and the CSV will provide 40 PSI constant while you are using water. With the CSV set just below the surface it would deliver 50 PSI constant while you are using water and would need a pressure switch setting of about 34/54.

I hope since you know the deadhead pressure with the CSV removed that you did not let an uneducated installer tell you the CSV was no good and just take it out of service? The CSV is a very simple valve and therefore doesn't cause any problems. When there are problems it is always because of something else, but the CSV usually gets the blame as the installer just doesn't know what he is doing. It is not that complicated and we are always here to help. But we can't do anything to help when the installer just takes it on himself to decide to put the CSV 20' deeper than it should be, just because he doesn't understand how it works and setting it 20' deeper is easier than cutting and threading a piece of pipe.

Your pump can build 100 PSI. So without the CSV it can easily reach 60 PSI even while you are using water. This will cause the pump to cycle on and off repeatedly while you are using water and have all the problems that go with cycling instead of just running steady as it will with the CSV.

My installer re-installed things as they were, with some grumbling of course. If I understand your pressure differential argument, swapping out for a CSV12560-1 will make the tank fill rate even slower after demand is shut off since the pressure differential will be 10 PSI smaller. It would allow higher PSI while water is flowing, but I don't know if there's a disadvantage there in terms of flow rate. Setting the pressure switch setting at about 34/54 makes me live dangerously close to the edge since a decrease in water level could cause the pump to run for > 2 minutes (forever?) at less than 1 GPM. This is not recommended by Grundfos. Their cutoff is about 3 GPM for extended running.

My goal is to have water pressure that cycles between 60 and 40. (Why is a separate issue). It seems that I have 2 choices:
1) Spend an extra $2K and get a bigger (3 hp) pump. Not sure if this would work. Negates any CSV operational savings.
2) Toss the CSV, since the current pump produces 100 PSI, get a bigger pressure tank and live with some extra cycling.

 

[Valveman]

That pump can run safely at 2/10s of a GPM forever and not be hurt no matter what Grundfos says. You have already heard form the Grundfos tech and you can tell he is not too bright.

The 60 PSI CSV will act just like a 50 PSI CSV when installed 20' below the surface. And I don't think you have to worry that the water level will drop so low that the pump cannot shut off at 54 or so. That is because when the pump is shutting off, the CSV is only letting it pump about 1/2 GPM, and at that low flow rate the pumping level will rise to the static level.

I don't think you need a larger pump. You just need the CSV to work at 50 PSI instead of 40 PSI.

 

[Reach4]

Why did leeelson's pressure not rise to the 60 PSI shut off after a few minutes?

 

[Valveman]

Why did leeelson's pressure not rise to the 60 PSI shut off after a few minutes?

I am sure it was rising. But only at about 1/2 GPM. I don't see where he ever told us what size tank he has. But an 80 gallon size tank with 25 gallons of drawdown would take 50 minutes to fill to 60 PSI with the CSV12550-1 set 20' below surface and acting like a 40 PSI valve.

 

[Reach4]

Observed pressure w/ CSV reaches 48. Tank is 8 gallons. Casing is 6". Riser pipe is 1- 1/4.

 

[Valveman]

With an 8 gallon actual size tank it should get to 60 in about 4 minutes. But getting to 60 isn't doing any good as it is going to work at 42 PSI with that CSV set 20' below surface.

 

[Reach4]

In reply #66, Leeeson said this:

This just in. Dead head pressure with CSV removed is 100 PSI.

Could it be that his bypass portion is somehow less open than it should be?

 

[Leeelson]

Some observations:
1) Nothing running. Pressure at 30, pump comes on. Pressure rises to 48 quickly, then slows. 5 minutes to 50, another 5 minutes to 52 (pressure switch was adjusted up to allow this). Experiment stopped. Lowest current draw is about 4.4= 1 KW.

2) Something running. Pump comes on at 30, takes 30 seconds to reach 48, 30 more seconds to reach 50.

3) Nothing running. Pressure rises to 44, then slows.> 5 minutes to 48.

Things don't seem consistent. At any rate, if it takes 5-10 minutes to even reach 48 or 50 PSI for each cycle, that's alot of power over the day (~.5 KWH) for filling the tank.

 

[Leeelson]

With an 8 gallon actual size tank it should get to 60 in about 4 minutes. But getting to 60 isn't doing any good as it is going to work at 42 PSI with that CSV set 20' below surface.

It doesn't come close. The best I could do is 52 after 10 minutes. Usually 48 is all it will do after 4 minutes. Defective CSV?

 

[Leeelson]

I don't think you need a larger pump. You just need the CSV to work at 50 PSI instead of 40 PSI.

How do I get pressure to vary between 40 and 60 PSI with a CSV, without it taking 5-10 minutes to reach 60 PSI?

 

[Valveman]

How do I get pressure to vary between 40 and 60 PSI with a CSV, without it taking 5-10 minutes to reach 60 PSI?

You don't. A 50 psi CSV that is set 20 feet below surface will only give you 40 psi no matter what you do. That is what it is suppose to do. If 40 psi is not enough to suit you then you need to move it closer to the surface and you will get 50 psi constant.

Then when no water is being used the CSV will fill the tank slower and slower as the pressure increases as that is decreasing the differential across the CSV.

I wish your pump man knew what he was doing and had installed that CSV closer to the surface to begin with. And that is still what is going to need to happen if you want 50 psi.

And no matter where the CSV is installed and no matter what pressure it is giving you when water is being used the pressure switch needs to be set to turn off the pump after it has been filling the tank for 2 to 3 minutes.

I can't just wave a magic wand from here and get your CSV moved to the proper location. And all the talking back and forth is not going to make the pressure higher. Somebody is going to have to install thw CSV properly.

 

[Leeelson]

You don't. A 50 psi CSV that is set 20 feet below surface will only give you 40 psi no matter what you do. That is what it is suppose to do. If 40 psi is not enough to suit you then you need to move it closer to the surface and you will get 50 psi constant.

Then when no water is being used the CSV will fill the tank slower and slower as the pressure increases as that is decreasing the differential across the CSV.

I wish your pump man knew what he was doing and had installed that CSV closer to the surface to begin with. And that is still what is going to need to happen if you want 50 psi.

And no matter where the CSV is installed and no matter what pressure it is giving you when water is being used the pressure switch needs to be set to turn off the pump after it has been filling the tank for 2 to 3 minutes.

I can't just wave a magic wand from here and get your CSV moved to the proper location. And all the talking back and forth is not going to make the pressure higher. Somebody is going to have to install thw CSV properly.

Just to set the record straight, the CSV was installed lower because there was no room for it at the surface. It might be possible to move it up some, but I'd like to know the likely result before investing the $300 to do that. Can I expect an extra PSI of static pressure for each 2.3 feet I move it up? Can I expect an extra 10 PSI of static pressure within 2-3 minutes if I replace the CSV with a 2560-1?

It was not obvious to me that a 50 PSI CSV even at the surface, would effectively limit the static pressure to 50 PSI. Maybe it should have been.

 

[Valveman]

Holding a steady 50 psi instead of letting the pump cycle continuously between 40 and 60 is wjat a CSV is suppose to do. That is why it is called a constant pressure valve. And that is how it makes pumps last longer and solve all the other problems associated with cycling.

If the pump man or somebody had called me before installing the CSV differently than the instructions specify, I could have saved you and me all this frustration. I don't think the pump man should charge for fixing something he installed incorrectly to begin with. There is no problem installing the CSV 20' lower, but it is going to give you 10 psi lower pressure.

Some pump guys will even do things like that on purpose so they can say "see I told you CSVs don't work". Some just don't understand what they are doing. But a constant 50 psi is better pressure and better for the pump and system than letting a pump cycle 40 to 60 over and over and over.