In article , (Harry K) wrote:

Now that you have had a batch of wrong, not to say bad, information,
here is the correct way.

Entirely correct. Good post, Harry -- I just have one improvement to suggest
below...


1. You have a bladder tank as shown by the 'tire valve' on the top.
The bladder has burst thus loosing your air bubble.
2. Proper way to drain and pre-charge the tank.
a. Shut pump off.
b. Open drain valve
c. Open a faucet somewhere in the system to allow air into the
tank.
d. When empty close all open valves.

I'd do this just a bit differently:

d. Start pumping air into the tank. When the water stops coming out, close all
open valves. You get it emptied faster and better that way.

e. Pump air into the tank until you have about 2 PSI -BELOW- the
cut-in pressure, i.e., if pump starts at 30psi, you want 27-28 psi in
the tank.
f. Restart pump.
g. Go around and open all faucets to release trapped air in the
pipes.

You really should replace the tank - they aren't that expensive.
There will be stagnant water trapped by the blown bladder that could
be mixing with your supply.

Harry K