Pressure tank calibration

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canyn

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This a friend's new location, I am looking to maximize water flow to the home. The setup will never be good...but it is what it is.

I don't know the pump particulars. There is a 57uf run/430uf (about) start cap in the box, so I'd guess the pump is in the 3/4hp range. The filed start card says the well is 235', tested to be 15gpm, drilled in '91. Pressure tank is a newer (not the original tank) Pentair. Didn't see a model number, but it's BIG..say 24" diameter and 72" tall, so 110 gallon or so with I'd suspect an approximate 35 gallon draw down, equipped with a 40/60 switch.

The home is 300' away, most important, it's at least 50' above the well. Line going into the ground is 1" poly.

Again, NOT my well, NOT my install. Having limited experience with water wells and systems, I would NEVER put the tank at the wellhead in such a situation.

My question: Does the pressure tank get setup the same considering the elevation difference. 'The same' meaning 2-3psi below the pressure switch 'on' setting when the tank is empty? The home water line needs to be shut off when doing that? Having 300' of 1" pipe running 50' uphill has got to be an issue if that plumbing is connected to the tank when calibrating the tank I'm sure. That seems obvious, but if I don't include it in the matter, someone will say, 'Is the home shutoff/separated from the tank?'

I don't know why the tank calibration would be different considering elevation...but maybe it should be.

Water pressure at the home is dismal, of course. Pressure calc equations I've used online show the system as installed to be pretty much hopeless. I'm looking to get it as good as it CAN get as it is. It's a rental.

First I looked at it, the tank cycle (from switch off/satisfied to on/running) was SEVEN gallons at the wellhead, the pump ran for less than 30 seconds. eww!

It will NEVER be good...but I'm hoping it can be better.

Thanks for the input!
 

Valveman

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The tank and pressure switch can be anywhere in the system. 50' of elevation is the same as 21 PSI. So, instead of the normal 40/60, you need to adjust the large screw (only) in pressure switch until the pump comes on at about 60 and off around 80 PSI. This will give you the normal 40 to 60 up at the house. The pressure tank will then need 55 PSI air charge, which is the only calibration of the tank that is needed.

Friction loss is figured at high flow rate, and a house usually uses less than 5 GPM. So, pipe size is not the problem.

With such a large tank the pump should run much longer than 15 seconds. Minimum run time required for the motor is 1 minute, 2 minutes is better, and running continuous is best.

Cycling on and off will be your only problem as the pressure will drop 20 PSI during each cycle. Using a Cycle Stop Valve set to maintain a strong constant 75 PSI will make so much shower pressure they will no longer need soap. Lol!


 

Reach4

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This setup may well be good after you have raised the pressure switch pressures.

I did not understand this: "First I looked at it, the tank cycle (from switch off/satisfied to on/running) was SEVEN gallons at the wellhead"

How did you measure 7 gallons? Turn off the pump, and measure the gallons from a spigot until the pressure switch kicks on again?

Air precharge is always measured and set with the water pressure near zero.

Pentair Wellmate pressure tanks are not so good. They use a bladder rather than a diaphragm. The bladder is theoretically replaceable when it fails. But the bladder (actually called the air cell) is less durable than a diaphragm.
 
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canyn

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This setup may well be good after you have raised the pressure switch pressures.

I did not understand this: "First I looked at it, the tank cycle (from switch off/satisfied to on/running) was SEVEN gallons at the wellhead"

How did you measure 7 gallons? Turn off the pump, and measure the gallons from a spigot until the pressure switch kicks on again?

Yes.

Air precharge is always measured and set with the water pressure near zero.

Yes...why I said, '...when the tank is empty.' ...the pre-charge process/figure.
Pentair Wellmate pressure tanks are not so good. They use a bladder rather than a diaphragm. The bladder is theoretically replaceable when it fails. But the bladder (actually called the air cell) is less durable than a diaphragm.

Yes. There is an old steel tank/diaphragm type that is sitting outside the pump shed. Evidently the contractor sold Pentair products. I'm not too impressed by the contractor. They bypassed the disconnect box. There is no way to reasonably disconnect power from the system, the sub-panel is a couple hundred feet away...through a blackberry bramble to boot.


Will a 40/60 control have a problem adding that much pressure? At some point I would imagine the diaphragm used in the control would be under duress. It not being my system, I'm hesitant to put that kind of pressure on the pump, too.

To the question: Is it a matter of correct procedure to isolate the tank from the uphill house (turn off the supply gate valve) during the pre-charge process. Seems an obvious 'yes' to me...but I don't know and is why I'm asking.
 

Reach4

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Will a 40/60 control have a problem adding that much pressure? At some point I would imagine the diaphragm used in the control would be under duress. It not being my system, I'm hesitant to put that kind of pressure on the pump, too.

To the question: Is it a matter of correct procedure to isolate the tank from the uphill house (turn off the supply gate valve) during the pre-charge process. Seems an obvious 'yes' to me...but I don't know and is why I'm asking.
Maybe. 3.5 turns CW will raise the pressures about 10 psi. If you can adjust, great. If not, adjust to what you can, and consider buying a pressure switch that starts out set to a higher pressure.

It is not normal to have a ball valve in the path between the pump and the pressure tank. It is normal to have a ball valve after the pressure tank and switch.


So normally you would close the valve, and then release pressure from the valve that drains the pressure tank. It might be a good time to flush the pressure tank.
Precharged Pressure tank flush:
1. Connect a hose to the sediment drain valve, and run that to where you plan to drain the water. I suggest filtering the output through a cloth if you suspect the sediment may include sand.
2. Turn off the pump.
3. Open the drain valve, and let it drain until the water stops. It would be possibly interesting to watch the first water that comes out.
4. Close the valve, and turn the pump back on, and let pressure build.
5. Repeat steps 2, 3 and 4 as needed.

If you use a pressure relief valve, most of those come preset to 75 psi. You would buy one preset to maybe 125 psi, or you would adjust a 75 psi valve by removing the cap and turning the screw (I think clockwise, but I have never done it).
 

Bannerman

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Is it a matter of correct procedure to isolate the tank from the uphill house (turn off the supply gate valve) during the pre-charge proces
Assuming the shut off valve is located after the tank & pressure switch, yes, close the valve to eliminate the back pressure caused by the water within the supply line feeding the elevated house.

Ensure the tank's drain valve remains fully open while adjusting the air pre-charge pressure. This will allow the additional air to push out any water that may remain within the tank's water chamber, and will also ensure there will be 0 pressure within the tank's water chamber while calibrating the correct pre-charge pressure.

Although a gate valve is superior to a globe valve, generally best to instead utilize a full port ball valve for that application. With a gate valve, the gate can become detached from the valve stem, thereby resulting in a substantial flow restriction through the valve, even as the valve appears to be fully open. That situation is far less likely to occur with a ball valve.
 
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