So I have a bit of a problem. I removed the under berth tank in the aft cabin and vented it out the same port as before. Filled the tank yesterday only to find the master cabin floor swelled up by a bloated water tank below.

Any idea why this would happen?

Could this be from excess pressure on my keel being as the boat is laid up transfering to the full water tank?

Just want to make sure I don't blow a hose or worse yet, rupture the tank!