12 Volt Pumps For Motorhomes, Caravans, Campers and Small Boats

Boats, caravans, and motorhomes use 12 volt pumps in several applications. Fresh water (Potable/drinking water) supply pressure and delivery is maintained by pumps. Sewage or effluent water may be removed with the help of a pump. But what type of pump should be used in a particular application?

All pumps work on the principle of creating a vacuum into which liquid is drawn. Liquid moves into the pump because of the air pressure on the surface of the large body of liquid into which the pump is placed or connected with by an intake pipe or hose. There are two basic ways in which that vacuum is created, and these differences are reflected in centrifugal pumps and diaphragm pumps.

Centrifugal pumps are very simple. A rotating impeller inside the pump forces water away from the centre of the passage, thus creating the vacuum. This design makes them cheap to manufacture, easy to maintain, and submersible. However, they are usually not self-priming, and can't handle many solids in the liquid matrix. They also cannot maintain an even pressure. There is a seal which prevents water from leaking into the motor. If these pumps run dry for very long the seal can be damaged.

Diaphragm pumps are larger and more complicated. They use a drive shaft to raise and lower a flexible diaphragm with each stroke. This changes the pressure inside the pump alternately opening and closing an intake and outflow valve, drawing water through. Diaphragm pumps require more maintenance, are not usually submersible because water should not contact the mechanical parts. They are initially more expensive. Diaphragm pumps are self-priming. Certain diaphragm pumps can handle dirty water and even debris because the liquid does not flow through the moving parts. They can also maintain a steady pressure, however without an accumulator tank water flow can pulse. Also, diaphragm pumps need to be mounted properly to prevent undue vibration.

Motorhome water pumps and caravan water pumps are usually centrifugal pumps. In addition to a submersible pump, an inline booster centrifugal pump can be added. Popular submersible brands of 12V pumps are the Whale GP881,Comet Elegant Immersion; Comet VIP Plus Immersion; and Comet GEO Plus Immersion. These range from a delivery rate of 8 litres/minute to 20 l/m. In size they vary from 38 to 43mm in diameter, making it an easy matter to slip them into the opening of water tanks. The Comet pumps have the ability to be run dry for up to 2 hours without damage, where as the Whale pumps strictly advise against being run dry.

Comet and Reich make inline booster centrifugal pumps. The delivery rate of these ranges from 11 to 18 l/m. These are slightly larger than the submersibles.

Diaphragm 12volt pumps for motorhomes and caravans are the Shurflo, Posiflo, and Fiamma. These pumps range in capability from 15 to 40 pounds per square inch pressure, at delivery rates of 7 to nearly 22 litres per minute. The largest of these is the Fiamma Aqua Pump capable of 10 litres per minute @21.75 psi (1.5bar). With a stainless steel filter and non-toxic parts these pumps are highly sanitary. They are resistant to deposits of scale and rust. Diaphragm pumps will not be damaged if it runs dry.

Marcle Leisure can supply various pump accessories such as additional filters, tubing, foot switches, non-return valves, expansion tanks (accumulators), and inline pressure switches.

Many 12 volt pump options are available from Marcle Leisure for caravan, motorhome, and small boat applications. By paying attention to the various types and brands of pumps and their capabilities the owner of a recreational vehicle can meet any need associated with the movement of liquids.

For a list of available pumps and their accessories, visit http://marcleleisure.co.uk

Steve_Monkley