What is that rule when dealing with water bladder tanks?

VERN in IL · #1 06/16/12, 11:15 PM

On a bladder pressure tank you need to have the bladder SLIGHTLY under the "working pressure", anyone know how many PSI's this is?

Say I'm running 40 p.s.i. "cutout" on the water pump, what pressure should my bladder be holding before I plumb it up?

Riverdale · #2 06/17/12, 04:40 AM

Most modern pressure tanks (like you would buy off the shelf today) are 'pre-charged'.

davel745 · #3 06/17/12, 05:37 AM

My tank says to be 2 pounds under the pressure. I add remove air with the tank empty to 36 to 38 pounds it seems to work well. My concern is calibration it is easy to be a few pounds off using equipment that is available ( water pressure gauge and tire pressure gauge).

wharton · #4 06/17/12, 06:23 AM

Quote:

Originally Posted by davel745

My tank says to be 2 pounds under the pressure. I add remove air with the tank empty to 36 to 38 pounds it seems to work well. My concern is calibration it is easy to be a few pounds off using equipment that is available ( water pressure gauge and tire pressure gauge).

Two lbs. is correct. That said, this is a set it, and forget it procedure. Concerns over gauge, and/or pressure switch calibration, or checking pressure in the absence of a problem, is a waste of time. It really isn't THAT critical to get it perfect, and it's not going to stay that way for long anyway.

VERN in IL · #5 06/17/12, 08:24 AM

Yeah I know they come precharged, but you have to adjust them to your pressure.

Ok, so you check the bladder pressure with the system unpressurized correct?

I would not say this is a set it and forget it. I have found with hard water and convertible deep well pumps, once the injector in the well gets some "buildup" of iron poop, the pump will not be able to sustain higher pressures and must be reduced or you will get prolonged runtimes....we never adjusted the bladder.

davel745 · #6 06/17/12, 08:28 AM

No I check the pressure at the tank and adjust it if necessary. I dont drain or bleed of air pressure i just adjust the air to about 2 pounds under water pressure.

Alice In TX/MO · #7 06/17/12, 08:59 AM

Here's a good article with some cautionary remarks as well.

Water tank air bladder pressure settings: How to Set or Adjust the Air Pressure in Bladder Type Water Storage & Pressure Tanks

agmantoo · #8 06/17/12, 09:02 AM

The correct PSI is 2lbs Under the turn on pressure/cut in pressure of the pump. The turn on/cut in pressure is not necessarily what the pressure switch is thought to be as it will change with time. If you have a momentarily cease or drop in water flow right before the pump kicks in you have the pressure set to high on the bladder tank or you need to recalibrate the pressure switch.

plowjockey · #9 06/17/12, 09:09 AM

I used to work for a plumber and never heard of normally having to readjust, either the pressure switch or the bladder tank.

If you have to go back and re-pressurize the bladder, the tank is usually about ready to be replaced, anyway.

arabian knight · #10 06/17/12, 11:11 AM

Quote:

Originally Posted by plowjockey

I used to work for a plumber and never heard of normally having to readjust, either the pressure switch or the bladder tank.

If you have to go back and re-pressurize the bladder, the tank is usually about ready to be replaced, anyway.

I have never heard of it either and coming from a lumping family myself.
And a few years ago my pressure switch went out. The plumber put in a new switch but never had to adjust anything else.

#11 06/17/12, 11:38 AM

Post # 8 is correct . To make it real simple have a working pressure gauge on the system . Watch the gauge to see what the pressure is when the pump turns on . Set the air pressure in the bladder tank to two pounds less than the pump turns on at . The bladder tank must be empty of water when setting air pressure in it .
If the pump turns on at 20 lbs . set the tank at 18 lbs . 30 pounds , 28 pounds , etc.

jross · #12 06/17/12, 12:45 PM

It depends on who set up the tank initially. My instructions say to shut off the pump, relieve the pressure by opening a faucet. pressure. Let the pressure decay until it reaches 5 psi or so, close the faucet. then charge the tank to the precharge pressure which on our tank is 20 psi. Start the pump and it should build up pressure until cutout. This will insure enough airspace in the tank to ease the burden on the pump. If you have to do this more than once a year, I'd say the bladder is leaking.