Just incase I walk away for a few minutes and get sidetracked. I've read many stories of people doing just that...then ending up with a mess. I'm only using 1/4" plumbing to and from my 14 gallon Rubbermaid holding containers. No float valve in the SW tank - if I fill it too much...it will go down the draindrsyme said:Why do you need an overflow from the SW tank? I would assume you would manually turn the valves so the water goes into that tank and would stay there until it is full and then shut it off. Besides is the volume of the tank that collects the water going to be signficantly higher than the SW tank? Are you planning on putting a float valve in the SW tank?