Question on pressure tank set pressure. Also pressure switch.

[viper1]

Have a brand new pressure tank I bought just as a temporary to be installed outdoors. It sits right next to the well. I ran some tests with it and maybe I have usually set things in the past and ran with them but I currently have the pressure switch set at 30/50, and pressure tank at 28psi (set when empty).

What I notice is pressure holds fine but as I bleed pressure off with the pump off, Pressure will drop to 28psi, then fall to 0 like NOW. I have reasoned that thr bladder will be at the bottom of the tank at 28psi so there is just no more expansive volume? So if I want a little more cushion around cut in, I was thinking to reduce tank pressure to 26psi? I realize this will fill the tank a little faster or different but I have had systems that see a sharp drop in line pressure just before the pump picks it up.

Also, I bought a "low pressure cut out" pressure switch that is supposed to cut the system at 10psi below cut in. I am finding that to be about 5 psi below. It is NOT adjustable or bypass-able. I was really hoping for a good layer of protection here but this seems like a POS. The vendor cannot tell me dick about it, the directions say nothing, etc. Are there any other low pressure cut switches I should consider? I am removing that switch and about to just install a standard switch.

 

[Reach4]

What I notice is pressure holds fine but as I bleed pressure off with the pump off, Pressure will drop to 28psi, then fall to 0 like NOW. I have reasoned that thr bladder will be at the bottom of the tank at 28psi so there is just no more expansive volume? So if I want a little more cushion around cut in, I was thinking to reduce tank pressure to 26psi? I realize this will fill the tank a little faster or different but I have had systems that see a sharp drop in line pressure just before the pump picks it up.

You are correct on all counts. If you have a jet pump, typically you would set the precharge to 26 or 25 psi. The 2 psi below cut-in is for submersible pumps, or multi-stage above-ground pumps. Jet pumps take a while to develop pressure.

Also, I bought a "low pressure cut out" pressure switch that is supposed to cut the system at 10psi below cut in. I am finding that to be about 5 psi below. It is NOT adjustable or bypass-able. I was really hoping for a good layer of protection here but this seems like a POS. The vendor cannot tell me dick about it, the directions say nothing, etc. Are there any other low pressure cut switches I should consider? I am removing that switch and about to just install a standard switch.

There are writeups on how to disable this feature by modifying the switch.

Dropping your air precharge should stop the false lockouts from your existing switch, but you still need to reset after loss of power. The pressure may have dropped by 10 psi so quickly, that you or your gauge did not pick up on that.

 

[Sponsor]

 

[viper1]

THANK YOU! This is a submersible pump but I am using it for construction purposes as well in which I will drive the pressure quite low at full flow. I need to bypass the low pressure cutout so the pump will keep running.

Can you direct me to a writeup? I am literally minutes from pulling that switch and rather leave it and make it work! In a normal application, It will probably work fine, but when I am demanding everything the pump has, I just cannot maintain the pressure.

 

[LLigetfa]

I lobotomized one a while back. I did not detail how but it was not difficult.
https://terrylove.com/forums/index.php?threads/frugality-at-its-finest.82903/
I wonder if @valveman has many EPS99 switches left over. Their low cutoff doesn't follow close to the cut-in like the Square-D do.
https://cyclestopvalves.com/products/electronic-pressure-switch-1

 

[Valveman]

Yeah I have plenty of those electronic pressure switches left. They have a low pressure setting of 10 PSI. But if you are trying to protect the pump from running dry, a low pressure switch is not the best way to do that. This is especially true if you are trying to run the pump wide open and let the pressure get low. It doesn't really matter where the low pressure switch is set, it will still trip at the same pressure as the air charge in the tank.

You can use a Cycle Sensor to protect the pump from running dry. It has nothing to do with pressure and will let the pump run at zero pressure as long as it is not pumping any air.

 

[Dystantthundr]

. Jet pumps take a while to develop pressure.

Glad to hear that, just replaced a waterlogged tank with same kind (35 gallon 38 precharge) new 60/40 switch. Was getting worried it was taking about 10 minutes to get back up to pressure. Might also look at cleaning the venturi.

 

[LLigetfa]

Glad to hear that, just replaced a waterlogged tank with same kind (35 gallon 38 precharge) new 60/40 switch. Was getting worried it was taking about 10 minutes to get back up to pressure. Might also look at cleaning the venturi.

That tank only holds about 10 gallons so a fill rate of 1 GPM is nothing to be glad about.

 

[Valveman]

Jet pumps do not take time to develop pressure. If the pump is primed it will develop pressure instantly like any pump. But if the pump is not primed it can take some time, which is not good. With a foot valve in the right location and a primed pump, pressure will develop in the blink of an eye. If it is slowly building pressure to the cut out point, the pump is primed but just not pumping as much as it should for some reason. Either the pump is bad or the well is not supplying enough water.