Fresh Water: Your Most Precious Tank

Recall from earlier cards that a boat is a set of closed systems you have to manage yourself — and none matters more day-to-day than fresh water. Water is stored in one or more tanks (often 100–400 litres on a typical 35–45 ft cruiser), usually built into the hull or fitted as flexible bladders low down so the weight stays near the boat's centre of gravity.

Getting water to the tap uses one of two methods. A pressurised water system runs an electric pump that switches on automatically whenever you open a tap, mimicking a house. Simpler or backup taps use a foot pump (or hand pump) — you physically pump each cupful, which draws no battery power and makes it almost impossible to waste water. Many cruisers keep a foot pump on the galley sink for exactly that reason.

The hard truth is that tanks are smaller than they feel. If four people each use 20 litres a day — a very frugal figure ashore — a 200-litre tank is empty in just over two days. So conservation is a skill, not an afterthought: take 'sailor's showers' (wet down, tap off, soap up, quick rinse), wash dishes in a basin of seawater and rinse with a splash of fresh, and catch the cold water while waiting for hot. Always know roughly how full your tank is, because a run-dry pump can suck in air and lose its prime.

A final habit: keep the tank topped up whenever you're at a dock with a hose. Full tanks mean more range between marinas — and, like ballast, water carried low actually helps the boat sit steady.