A few weeks ago I have my pitless adapter replaced. Since then, I have had intermittent low pressure issues. Typically when two showers are going at the same time, or when my acid neutralizer and a shower are both on. Never had this issue prior to replacing the pitless.

Since then I have replaced the pressure switch (30-50psi) and gauge, and the problem still exists. My pressure tank is ok, I think- tested the pressure and it is at 27psi. Banging on the tank it is "tinny" sound at the top, very "dull" sound at the bottom. Tested the new pressure switch, and it is reliably turning cutting in at 30 and cutting out at 50.

I have a check valve and since the house holds pressure all night, I figure there may be either a leak between the check valve and the pump, or the pump isn't delivering the pressure required to run 2 showers at the same time. I dug a trench down to the pitless to re-inspect the work (thinking the pressure of the dirt dislodged the pipe from the pitless fitting), and it is all snug and tight- no issues.

When the pitless was replaced, the plumber replaced a 3 foot section of the pipe coming to the house, adding an extra coupler in the process. Could the coupler be restricting flow? Also, the plumber cut about 3 foot of pipe between the pitless and submersible pump. Could I have a shallow well and this 3 feet made a difference?