My pool is 16 x 38 fiberglass, 3.5 to 6.5 deep. (I don't know the size of the pipes.) The psi has been at 20-22 since opening. I thought it was at 12 last summer but can't really remember. The gauge goes to zero when off so I don't think it's a bad gauge.
Is 20 psi too high? If it is, what does that mean?