A relative claims to have fixed the overflowing tank. He said there were two valves at the bottom of the tank, one of which should have been closed. He closed it, which fixed the problem. He said that the way the plumbing was set up, the pump was trying to build a head of pressure in the tank, so it was overflowing. I don't fully understand and will try to diagram the system for myself next time I am up there. But he went back a week later and it had not overflowed again and was beginning to dry out.

Hope this makes sense.

Thanks for all your help! Your thoughts allowed me to talk to him about the problem relatively coherently before he went up there.

Congratulations on the fix. Thanks for the up date, all too often we never hear the end of the story.