Sorry, Jack...not true.
If there were a leak DOWNstream of the pump, the only thing that would happen at a faucet is reduced pressure due to the leak...it wouldn't just spit air. And the leak would be easy to find, 'cuz a) water would be spurting out of it...and b) it would drain your water tank. Only one thing can cause a diaphragm water pump to run continuously and spit air out a faucet instead of water: it's trying to prime and can't--because it's sucking air instead of water. When the water level in the tank drops below the top of the discharge port, that'll cause it...and so will a failed diaphragm...'cuz when the diaphragm fails, the pump sucks air through the tear in it and can't prime. Jeff is sure his water tank is full, so that leaves only one possibility: the diaphragm in the pump has failed. Usually there's some warning...as the diaphragm starts to go, the pump starts cycling for a few seconds for no reason. As the tear gets bigger, it cycles more often and runs longer...till finally it starts running continuously. The time to replace the diaphragm is when the symptoms first start...'cuz Murphy being Murphy, it will choose to quit pumping water altogether an hour before you're expecting guests aboard for a dinner cruise--which is when mine did. Cost me $90 for new pump, 'cuz I had enough time to run to WM for a new new pump and swap 'em out before they arrived, but not enough time to take it apart and fix it. So pay attention what's happening on your boats. A "new" noise--or absence of a usual one--ALWAYS means something...and it's usually cheaper to find out what it is early than after it fails altogether.
