Does anyone know how many gallons the fresh water tank holds? Mine has not been used in years and I need to recommission (found the proper technique to do so in a post from Peggy here). I am also replacing the sink drain seacock (old gate type) with a ball valve model. It's a pump faucet system so it will take a lot of work to purge/rinse/rerinse - is there an easier way, perhaps using a wet vac to the faucet hose connection? thanks for any suggestions mike