Adjusting Air Pressure in Well Pressure tank

Question

I need to refill my air pressure in a well pressure tank and have received conflicting reports on how to drain the tank. Some say that the tank has to drain completely (from the valve at the bottom of the tank) in order to fill the air pressure to 38PSI (40/60 pressure) and others say just to open a faucet in the house until water stops coming out.
The tank is in the basement, so a faucet on the first floor still means there is water pushing down into the tank when when stops coming out, so I wasn't sure if that was enough to add air to the tank.

Ed Beal · Answer

With the tank in the basement you will need a few extra psi to fully push all the water out.
Many pressure tanks are on the same level as the faucets. You can do it either way but remember you have 8-10’ column of water of back pressure so where you might be 2 psi below the cut in pressure with the additional water column pressure you may need to be just over the pressure to use the total volume of the pressure tank so 42 psi may be needed to get full draw down. Open the water spigot upstairs and add air , the difference of draining below and above is about 4 psi so take the tank to 42 psi with the upstairs faucet open if it holds your bladder or diaphragm is good. If the faucet starts blowing bubbles and you loose the air pressure at the tank it needs a new bladder or replaced.
In reality it’s not a big deal unless you have a small tank.

Adjusting Air Pressure in Well Pressure tank

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