won't hold pressure

Another newbie here,

Two days ago, I heard my well pump kick on and was puzzled because it was late and no one was using any water. So I watched the pressure gauge drop from 50 psi to 30 psi in about 50 minutes - again no one using water - and the pump kicked on again. When I shut off the main valve, pressure stayed constant. I shut every valve to every faucet I could get to (except the 2 bathtubs don't have access/shutoffs) and opened the main. Again, pressure dropping. I don't see any evidence of leaking water in the house. After 2 days, if I had a leak, it would have shown itself, right? I can hear water moving (no leaking) through the plasitic water softener inlet/outlet port (a slight hissing/trickling sound) which stops when I shut off the main valve.
Plumbing is original to 10+ year old house.

Could anyone offer help or advise, please. Thanks in advance.

Leaking toilet tank valve maybe? Add a little food color to the tank and see if any gets to the bowl during non-use.

If your plumbing is under a slab foundation, I may have some very bad news for you.

Mikey's right about that. With copper plumbing and chlorinated water, big expense when the copper starts with the pinhole thing.

bob...

Mark64 said:

I can hear water moving (no leaking) through the plasitic water softener inlet/outlet port (a slight hissing/trickling sound) which stops when I shut off the main valve.

Click to expand...

Check the (either) end of the softener drain line for water running (you can take it off the softener if you can't get to the far end). If there is water running out to drain, then put the softener in by-pass, you've found your leak.