Pump won't make cut off pressure, pressure tank acting strange

[AngryYJ]

Hi everyone!
First time living in a house with a well and we started experiencing a problem.

I have a deep well with a submersible pump at 46ft feeding a 30gal pressure tank being ran off a pentek intellidrive VFD. My wife called me at work the other night that there was no water in the house and the VFD showed "Pipe break" fault. The system is set for 60 psi setpoint with 15psi cut in, however the pump was running constantly unable to make over 52psi.

Currently I verified that no leaks are present by isolating the hand valves supplying the house and irrigation lines and the pump still couldn't build 60psi.

I ended up dropping the setpoint to 40 psi and the pump can maintain that. I started looking into the pressure tank and emptied the water from it and found the air charge to be at 15psi. I pressurized it to 23psi, which is 2psi shy of the cut in of 25psi.

However, when draining the tank it drains 5 gallons of water while slowly dropping from 40psi and then abruptly stops around 20psi, sending the gauge right to 0psi. If I give the tank a shake it sounds like there is still water in it and when I shut the spigot, the pressure gauge climbs slowly back up to 24psi.

Is it safe to say this tank is junk? Pinhole of air bleeding past the bladder? Or is this normal and the gauge is just showing the air charge pressure? The pressure tank spec shows a spec of 8.9gal drawdown and I only pulled 5 gallons.

I'm really hoping this is the root cause of not being able to reach 60psi, but Im unsure if this could cause that. I'm hoping that I don't have to replace the well pump due to it being weak from the pressure tank not being set up correctly.

All advice is appreciated as I'm new to well systems!

Thanks.

 

[Sarg]

I suspect the bladder on the tank is leaking if you have water within after being drained to zero.
Also confused by your statement that your pressure switch is "set" ....so it is on at 15 and shuts off at 60 psi. That is a 45 psi range and I thought the switch range was pretty much limited to about 20 psi. ( 30/50 - 40/60 - etc. )
If your range is really set that far apart ... below is a prior post from the Valveman in 2021. ( Copy & pasted )

Any more than a 20 PSI differential will stretch the bladder/diaphragm too far

 

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[AngryYJ]

I suspect the bladder on the tank is leaking if you have water within after being drained to zero.
Also confused by your statement that your pressure switch is "set" ....so it is on at 15 and shuts off at 60 psi. That is a 45 psi range and I thought the switch range was pretty much limited to about 20 psi. ( 30/50 - 40/60 - etc. )
If your range is really set that far apart ... below is a prior post from the Valveman in 2021. ( Copy & pasted )

Any more than a 20 PSI differential will stretch the bladder/diaphragm too far

Sorry, I should have phrased that better. 15psi differential. Pump starts at 25psi, stops at 40psi. It originally was 60/45 before the pump failed to make 60psi

 

[Valveman]

Hi everyone!
First time living in a house with a well and we started experiencing a problem.

I have a deep well with a submersible pump at 46ft feeding a 30gal pressure tank being ran off a pentek intellidrive VFD. My wife called me at work the other night that there was no water in the house and the VFD showed "Pipe break" fault. The system is set for 60 psi setpoint with 15psi cut in, however the pump was running constantly unable to make over 52psi.

Currently I verified that no leaks are present by isolating the hand valves supplying the house and irrigation lines and the pump still couldn't build 60psi.

I ended up dropping the setpoint to 40 psi and the pump can maintain that. I started looking into the pressure tank and emptied the water from it and found the air charge to be at 15psi. I pressurized it to 23psi, which is 2psi shy of the cut in of 25psi.

However, when draining the tank it drains 5 gallons of water while slowly dropping from 40psi and then abruptly stops around 20psi, sending the gauge right to 0psi. If I give the tank a shake it sounds like there is still water in it and when I shut the spigot, the pressure gauge climbs slowly back up to 24psi.

Is it safe to say this tank is junk? Pinhole of air bleeding past the bladder? Or is this normal and the gauge is just showing the air charge pressure? The pressure tank spec shows a spec of 8.9gal drawdown and I only pulled 5 gallons.

I'm really hoping this is the root cause of not being able to reach 60psi, but Im unsure if this could cause that. I'm hoping that I don't have to replace the well pump due to it being weak from the pressure tank not being set up correctly.

All advice is appreciated as I'm new to well systems!

Thanks.

Sorry for your problem. If a normal dumb pump is still good, the simple pressure switch sends it power and it comes on and runs. If the motor is bad, it pulls high amps and trips the overload. With a variable speed system like the Pentek VFD there are thousands of computerized components and software, which leaves thousands of opportunities for a failure. I agree your tank is probably bad. But probably not what is casing the problem.

Checking for a leak down the well you can turn power off to the pump. With all valves closed to the house and no check valve at the well head or tank, the pressure will leak off if there is a hole down the casing.

It would not surprise me for a pump installer to think they are brilliant for thinking a VFD is superior and knowing how to program the 15 PSI sleep mode and all that stuff, then not know a little electric tape on the metal connection to the pump is needed to keep electrolysis from quickly eating a hole in the fitting.

 

[AngryYJ]

Sorry for your problem. If a normal dumb pump is still good, the simple pressure switch sends it power and it comes on and runs. If the motor is bad, it pulls high amps and trips the overload. With a variable speed system like the Pentek VFD there are thousands of computerized components and software, which leaves thousands of opportunities for a failure. I agree your tank is probably bad. But probably not what is casing the problem.

Checking for a leak down the well you can turn power off to the pump. With all valves closed to the house and no check valve at the well head or tank, the pressure will leak off if there is a hole down the casing.

It would not surprise me for a pump installer to think they are brilliant for thinking a VFD is superior and knowing how to program the 15 PSI sleep mode and all that stuff, then not know a little electric tape on the metal connection to the pump is needed to keep electrolysis from quickly eating a hole in the fitting.

I have shut the valve to the house and pressure has stayed steady at least for a 10 min check.

I have also pulled the we'll head and verified the pitless adapter isn't leaking. It doesn't appear to be in the tubing either, however you can only see so much down a well...

The VFD pulls around 4-5 amps but I haven't checked for initial spike at pump start with an ammeter. It does flicker a warning for service factor amps upon pump startup.

I have a feeling the pumps on its way out, but I'm hoping that's not the case. I have no idea what size pump is in it to even reference and test resistance and amp draw.

Either way, it sounds like a pressure tank is in my future first, and hope it didn't overwork and cause my pump to get weak.

 

[Valveman]

If there is a second check valve anywhere before the pressure tank it will prevent the water in the tank from going back to the leak and the pressure will not fall. There should be little if any amp spike on start up with a VFD. But that could be the problem. Submersible motors that are started too slowly will have premature bearing damage. That VFD cannot be very old, so I hoe the pump is still OK. But VFD's are not known to last very long and are not good for the pump/motor either. That is exactly why so many pump guys like them. They give lots of repeat business when a simple dumb pump might run 30 years with no maintenance.

You will also have a three phase motor as is needed to work with that VFD. Even if the pump end is the problem, changing to a normal pressure switch system will require replacing the motor as well, as you will need a single phase motor to work on regular house current.

But again, it could be the VFD is not speeding up the pump or any of a hundred different possibilities. Gonna need a smart pump guy to figure out the problem. But an even smarter pump guy would not use a VFD.

 

[AngryYJ]

If there is a second check valve anywhere before the pressure tank it will prevent the water in the tank from going back to the leak and the pressure will not fall. There should be little if any amp spike on start up with a VFD. But that could be the problem. Submersible motors that are started too slowly will have premature bearing damage. That VFD cannot be very old, so I hoe the pump is still OK. But VFD's are not known to last very long and are not good for the pump/motor either. That is exactly why so many pump guys like them. They give lots of repeat business when a simple dumb pump might run 30 years with no maintenance.

You will also have a three phase motor as is needed to work with that VFD. Even if the pump end is the problem, changing to a normal pressure switch system will require replacing the motor as well, as you will need a single phase motor to work on regular house current.

But again, it could be the VFD is not speeding up the pump or any of a hundred different possibilities. Gonna need a smart pump guy to figure out the problem. But an even smarter pump guy would not use a VFD.

It for sure is a single phase, 2 wire pump. There is no check anywhere in the line prior to the pressure tank.

 

[Valveman]

Ahh OK, it is a "PID" by Pentair. Yes, those use a 2 wire, single phase motor. I understand now why the tank bladder is bad. Those type VFD controllers will ramp up and hold the pump speed needed to maintain 60 PSI constant. But the way I understand they only hold constant pressure for 60 seconds. If the flow rate doesn't change in 60 seconds they let the pump go to sleep (half speed), the pressure tank then supplies the water needed until the pressure drops 15 PSI, then the pump is ramped up again. This process is repeated over and over when water is used for extended periods of time. I know this is hard on a tank bladder, going up and down with each pump cycle, but I don't know how it effects the longevity of the pump/motor itself. With other brands of VFD's that work this way I have seen pump shafts and couplings broken, as well as impellers spun off. I guess ramping up and down every minute is better than cycling completely off every minute, but I still so not see how it is good for the for several reasons.

My guess is if the pump fails to reach the target pressure it is not spinning fast enough. There maybe some dip switches or something in the PID where you can adjust maximum hertz or RPM. I would think that if it is running at max speed of 3450 RPM and still not reaching the set point, it would at least be drawing max amps for that size motor. If it is not drawing max amps, it is probably not running at max RPM.