[Carl n Susan]

That tank has to be in the 40 gallon range. Filling up each day for two days is a lot of water. I think the only fixtures that drain into it are the faucets in the kitchen and sink. I would first open the drain (close the others) with a clear plastic connector to see if there is a constant stream of water emanating. Obviously there should not be ant if the faucets are off. If there is then something else is draining and needs to be found.

If no water is running out, then the questions is how much water are you running washing dishes? A continuous stream can use a lot of water. Not that it is a real problem, many of us leave that drain valve open all the time so we don't have to worry about filling the tank.