Is it only at the shower? What about the sink next to it, or any other fixture(s) in the house? What kind of shower valve? Moen? Symmons? Kohler?We are on a well and the water comes in, through a pressure system to the water tank. (of course cold is seperate). When taking a shower, the water is cool until the hot kicks in at the showerhead level. The hot is too hot so we turn it down to a comfortable level. After about 90 seconds the water gets hotter once again. Doesn't make sense to me. Can someone explain what might be the cause? Thanks.
If this is happening only at that one shower valve, I suspect the stem/cartridge, or "balancing spool" (depending on the make of the valve) needs to be replaced.