30-gallon is standard in most of our campers if you have a shower but you have a choice or 30, 16 or 10 gallon tanks. In a camper with sink only, 10-gallon tanks are adequate.  WE also offer a hand pump faucet option that requires no water tank at all.  With a hand-pump sink you will get our standard stainless-steel sink basin and a hand-pump faucet tied to a feeder hose that runs down into the cabinet below. You may feed the tube into any liquid source to pump through your sink faucet.