i am on cistern water adn we have been going through a lot of water. i have been down in the tank and can find no evidence of a leak in the cister, no tears or bulges where water would be hiding behind the plastic liner. i suspect the galvanized pip going into the house is leaking. is there a way to pressure test this line? if it is leaking can i just run a smaller diameter pvc through the galvanized?

thanks for any help in advance.