I have cloudy red water in the water from the pressure tank. How do I purge the system to get rid of any sediment in the tank and what air pressure should be maintained in the tank?

The tank you are using tends to "purge" itself, assuming it has the opening at the bottom like most tanks. The cloudiness in the water is coming from the well, not the tank.

As for pressure, set the tank pressure at 2# BELOW the cut in pressure. So, for instance, if your system cuts on 30#, then you will set the tank pressure at 28#. Do this with the system off and pressure drained to zero by opening a low level faucet.

If you have a galvanized tank, then that is a different story. Is that the case?

Assuming you are referring to a bladder tank (painted), not a galvanized pressure tank (not painted).

Well pressure switches normally come from factory set to a 20 lb. pressure differential. That is, there is 20 lbs. difference between cut on and cut off pressures. They usually come 20-40, 30-50 or 40-60. However, they are all the same switch and can be adjusted to your preference.

Your bladder tank air pre-charge should be set to 2 lbs. less than the cut on pressure. If your switch is set to come on at 30 lbs. your pre-charge should be 28 lbs. That way your pump will come on just before you run out of water in the tank. The pre-charge is set with the tank empty of all water.

It is unlikely that you have any sediment in the tank. The pump comes on and fills the tank. Granted the water sits there in the tank until you use it and any sediment would settle to the bottom. But the water is pumped into the bottom of the tank, actually into the bladder, and it also comes out the bottom. Therefore any sediment would come out as you normally use water.

In other words, to flush the tank you simply open a faucet and let it run. Note however that once the pressure drops, and the pump comes on, the water will be coming directly from the well not from the tank.

If you are experiencing discolored water when you first open a faucet, you probably do have some sediment settling to the bottom of the pressure tank, but is is being flushed out each time you open the faucet.