Help - Submersible pump and tank sistem pressure drop

[underpressure101]

Hi everyone.

I have the following situation with a submersible pump and tank sistem.

The pressure switch starts the pump when the pressure reaches 30 psi, then when the needle of the pressure gauge reaches 50 psi the pressure switch stops the pump and immediately the pressure drops around 45 psi and remains there. I also closed the valve that feeds water to the house so no water leaks from the house, only the pump and the tank and let it overnight to see if pressure drops further, and is not.

What should I do to fix this? I can't find any leaks and the tank is ok. To me a pressure drop like 1.5 psi may be normal but 5 psi seems too much.

I also attached a picture: https://workupload.com/file/xhcUgLeVprW

 

[Reach4]

The pressure switch starts the pump when the pressure reaches 30 psi, then when the needle of the pressure gauge reaches 50 psi the pressure switch stops the pump and immediately the pressure drops around 45 psi and remains there. I also closed the valve that feeds water to the house so no water leaks from the house, only the pump and the tank and let it overnight to see if pressure drops further, and is not.

What should I do to fix this? I can't find any leaks and the tank is ok. To me a pressure drop like 1.5 psi may be normal but 5 psi seems too much.

I think there is significant pressure drop between the pressure switch and the pressure tank. Your pressure switch sees more pressure than the pressure tank sees, because you have a small path to the pressure tank. So pressure switch cuts off, and the pressure tank continues to take a little extra water.

 

[Sponsor]

 

[underpressure101]

I also thinked that but what confuses me is that if I close the output valve and force the water to go only to the tank the same happens. Should I redo everything and the pipe from the pump go straight to the tank and place the pressure switch there? Could this happen if the pump is to powerfull and the tank needs a small time to "adjust" ?

 

[Reach4]

I also thinked that but what confuses me is that if I close the output valve and force the water to go only to the tank the same happens. Should I redo everything and the pipe from the pump go straight to the tank and place the pressure switch there? Could this happen if the pump is to powerfull and the tank needs a small time to "adjust" ?

Closing the valve does not make the effect less.

A CSV before the pressure tank and pressure switch would solve this by making the flow slow before the pressure switch approached cut-off.

You would probably also have the ability to go to a 40/60 pressure switch, or stay with 30/60.

 

[Bannerman]

The connection to your pressure tank appears much smaller in diameter compared to the pipe supplying water from the pump. The smaller diameter connection will restrict and therefore, slow the flow rate of water entering the tank.

In order to work properly, any pump while running, will need to be capable of building higher pressure than the pressure switch cut-off setting. With restricted flow into the tank, the pressure switch will be sensing the pressure delivered directly from the pump, so once the pressure switch senses 50 psi, it will shut down the pump, even as the tank had not yet filled fully to 50 psi.

It is the pressure tank which stores pressure from the pump, and it is that stored pressure that maintains pressure in the system while the pump is not running. Although the pressure switch correctly shut down the pump when it sensed 50 psi, due to the restricted flow, the tank had been only filled to 45 psi, so the system pressure immediately dropped to 45 psi, equal to the pressure stored within the tank.

What should I do to fix this?

Without a CSV, the correct fix will be to eliminate the restriction by replacing the tank and piping, upgrading to ensure the connections are equal to or larger in diameter to the supply pipe from the pump., thereby permitting water to flow into the tank as rapidly as the pump is supplying.

As R4 suggested above, an upgrade to your system will be to install a Cycle Stop Valve (CSV). By using a CSV, you should not need to replace your exsting tank or piping as a CSV, in addition to multiple additional benefits, will reduce the flow rate from the pump to only 1 gpm while the final 50% of the pressure tank's capacity is being filled. I'm confident your existing tank and piping, will have no issue flowing 1 gpm or greater with no restriction.


CSV Interactive Animation

 

[RetiredInGueydan]

Hi everyone.

I have the following situation with a submersible pump and tank sistem.

The pressure switch starts the pump when the pressure reaches 30 psi, then when the needle of the pressure gauge reaches 50 psi the pressure switch stops the pump and immediately the pressure drops around 45 psi and remains there. I also closed the valve that feeds water to the house so no water leaks from the house, only the pump and the tank and let it overnight to see if pressure drops further, and is not.

What should I do to fix this? I can't find any leaks and the tank is ok. To me a pressure drop like 1.5 psi may be normal but 5 psi seems too much.

I also attached a picture: https://workupload.com/file/xhcUgLeVprW

Set the pressure switch to 30/55.

 

[Reach4]

Set the pressure switch to 30/55.

Adjust the differential nut if you want to raise or lower the
cut-out setting while keeping the cut-in pressure constant. The
differential nut is the 3/8-inch nut that adjusts the smaller of
the two springs in Models FSG, FYG, FRG, and Type G switches. Turn
the differential nut clockwise to increase the cut-out pressure and
counter-clockwise to lower the cut-out pressure. Adjusting the
differential nut will change only the cut-out setting while the
cut-in setting remains unchanged.

So underpressure101, if you wanted to implement this work-around, you would turn the nut on the smaller spring clockwise. I don't know if the right amount of turns to raise cut-off by 5 psi would be 1.75 turns CW. The stuff I read does not say what expected rise for this differential nut is. Maybe start with 1 turn, and see what the effect is.

This workaround will be less consistent than other methods I think, but it is free. I am thinking that if you are using a lot of water, the quick-shutoff problem would be less, so you could end up with higher pressure than you want.

 

[underpressure101]

The problem I think it starts from the pump. I misjudged the pump and its too powerful for my system. The water flow is too high. I don`t want to buy another pump so for the moment I will adjust the pressure a little bit.

 

[SuperGreg]

Why is the connection to the tank so small? Typically you would want a 1"+ connection to the tank with the pressure switch right on that pipe or a manifold connected to that pipe. What size tank is that? Looks small enough that it will cycle like crazy without a CSV.

 

[Valveman]

The problem I think it starts from the pump. I misjudged the pump and its too powerful for my system. The water flow is too high. I don`t want to buy another pump so for the moment I will adjust the pressure a little bit.

All pumps are too powerful for the demand. That is what a CSV is for. The CSV makes a large pump act like a small pump when needed and still allows full flow as needed as well.