Thanks for replies

I had the original installer of the iron filter come out

Pulled the drain hose off and water poured out non stop.

Pulled the tank piston and replaced the seals but the piston is still leaking and he doesn't have replacement till next week.

So he has put the filter into bypass which has stopped the leaking and psi loss.

He said I should be good for the weekend in bypass till early next week till he can get a new tank piston