On a motor yacht or sailing yacht, four discrete plumbing systems are packed into the below decks area.

1. The Fresh water system supplies fresh water for drinking, cooking and washing to a galley sink. A hand pump on the sink or an electric water pump draws the water from a tank, usually positioned in the bow to counterbalance the weight of other heavy installations farther aft. This tank is vented, allowing air to enter as the water level changes; otherwise, a vacuum left by departing water would make pumping difficult. The waste water from the sink flows out of the boat by gravity; the outlet is located just above the waterline so that dirty water does not dribble any appreciable distance down the hull
2. A second system, called the Marine Head (toilet) system, provides raw water for the toilet. A pump beside the toilet draws water through a seacock at the bottom of the hull and, depending on the age of the boat, flushes it either overboard or, as is now common practice on bareboats used on yacht charters in the Whitsunday Islands that toilet waste is flushed into a vented holding tank that is emptied when the bareboat leaves restricted anchorages.
3. In the third system, another seacock admits raw sea water to cool the engine. After the cooling water has passed through the engine block, the system's pump, powered by the engine itself, expels the water via the exhaust pipe along with the engine's exhaust gases.
4. The fourth - and the simplest - Bilge Pump System pumps out any water that has collected in the bilge. A strainer-covered hose end resting in the deepest part of the hull sucks up the water through a pump and discharges it overboard through an outlet near the waterline.

A seacock controls the flow or raw water into toilets or engine-cooling systems by a rotating valve that opens when the handle is vertical and closes when it is horizontal.

The fresh water system

All bareboats are fitted with two or three fresh water tanks of varying capacities.

Generally, the water flow from these tanks is controlled through diverter valves allowing you to use the tanks progressively.

To maintain boat trim, use any stern tanks first... using the bow tank last keeps that weight of water forward, until the stern tanks empty.

Pressure system

Bareboats generally operate with a fully pressurised hot and cold water system...for this system to operate you need to turn on the fresh water pump which operates on 12v power. If you hear this pump running and you are not using water (all taps closed)...switch off the pump immediately... before the pump and impeller are damaged, look for the reason. You can review a long list... Refer to Fresh water pump trouble-shooting chart.

1. You are out of water in the tank you are using...turn diverter valve to an unused water tank.
   
2. You have a leak in the supply line from the pump to the taps... after locating leak, repair if possible after isolating that section.
   
3. The pressure switch is faulty... report to your charter operator.

Hot water cylinder

The hot water system on your bareboat almost always works through a heat exchange connected into the main engine. The water automatically heats when the engine has run for approximately 20 minutes. Water will stay hot in the insulated hot water cylinder for a considerable period. Best time to have a shower is during or directly after the motor has run.

When connected to the 240 volt shore power at a Marina, the water is heated (on some bareboats) by turning on the 'Water Heater' switch on the 240 volt switchboard.

Refilling fresh water tanks

In the Whitsundays, Abel Point Marina in Airlie Beach or Shute Harbour are the only places you can be certain your fresh water tanks can be refilled with water of good quality...so use sparingly.

Your fresh water hose is often attached to a sea water valve and used to hose down the boat or anchor... because this hose is used with sea water, flush fresh water through, before you fill the fresh water tanks.

Filler caps are marked 'water', make certain you only put water into these locations as this can have immediate and expensive consequences if you mistake the 'Diesel fuel' filler cap.

Shower

It is recommended that all crew on a bareboat yacht charter restrict themselves to a maximum of 2 minutes of water time per person per day.

By wetting yourself down then turning off the water while soaping, you will find you have ample water to rinse.

On most bareboats the shower and hand basin water drains into a sump which operates on a float or pressure switch that automatically pumps out the water.

Fresh water pump troubleshooting chart