I already replaced the pressure switch. I am only getting 30 psi with the deep well pump constantly running. It will not build up pressure.

When you turn off the pump at the breaker, will it hold 30#?

It will not get past 21# psi. There is a gauge before the tank. When you turn on a faucet the pressure drops. The max is 21 #. I replaced the pressure switch. It is a 40-60 switch. The pump stays on constantly but will not build up. Very low pressure upstairs. Cannot take a shower up there. SHOWERS only in basement.
Thanks

There are several possibilities:

1. There is a leak somewhere, either in your wellpipe, or "upstream" toward the house. The house side is not likely as you would doubtless notice it.

2. Pump going bad. How old is it?

3. Not likely, but the water table could be down to the point where the pump is not sitting in much depth of water and ends up pumping part air, part water.

How far down is it to the pump?

The switch and pressure tank are not your problem so don't waste money replacing them.