| Boats, caravans, and motorhomes use 12 volt | | | | diaphragm pumps need to be mounted properly |
| pumps in several applications. Fresh water (Potable | | | | to prevent undue vibration. |
| drinking water) supply pressure and delivery is | | | | Motorhome water pumps and caravan water |
| maintained by pumps. Sewage or effluent water | | | | pumps are usually centrifugal pumps. In addition to |
| may be removed with the help of a pump. But | | | | a submersible pump, an inline booster centrifugal |
| what type of pump should be used in a particular | | | | pump can be added. Popular submersible brands |
| application? | | | | of 12V pumps are the Whale GP881,Comet |
| All pumps work on the principle of creating a | | | | Elegant Immersion; Comet VIP Plus Immersion; |
| vacuum into which liquid is drawn. Liquid moves | | | | and Comet GEO Plus Immersion. These range |
| into the pump because of the air pressure on the | | | | from a delivery rate of 8 litres/minute to 20 l/m. |
| surface of the large body of liquid into which the | | | | In size they vary from 38 to 43mm in diameter, |
| pump is placed or connected with by an intake | | | | making it an easy matter to slip them into the |
| pipe or hose. There are two basic ways in which | | | | opening of water tanks. The Comet pumps have |
| that vacuum is created, and these differences are | | | | the ability to be run dry for up to 2 hours without |
| reflected in centrifugal pumps and diaphragm | | | | damage, where as the Whale pumps strictly |
| pumps. | | | | advise against being run dry. |
| Centrifugal pumps are very simple. A rotating | | | | Comet and Reich make inline booster centrifugal |
| impeller inside the pump forces water away from | | | | pumps. The delivery rate of these ranges from 11 |
| the centre of the passage, thus creating the | | | | to 18 l/m. These are slightly larger than the |
| vacuum. This design makes them cheap to | | | | submersibles. |
| manufacture, easy to maintain, and submersible. | | | | Diaphragm 12volt pumps for motorhomes and |
| However, they are usually not self-priming, and | | | | caravans are the Shurflo, Posiflo, and Fiamma. |
| can't handle many solids in the liquid matrix. They | | | | These pumps range in capability from 15 to 40 |
| also cannot maintain an even pressure. There is a | | | | pounds per square inch pressure, at delivery rates |
| seal which prevents water from leaking into the | | | | of 7 to nearly 22 litres per minute. The largest of |
| motor. If these pumps run dry for very long the | | | | these is the Fiamma Aqua Pump capable of 10 |
| seal can be damaged. | | | | litres per minute @21.75 psi (1.5bar). With a |
| Diaphragm pumps are larger and more | | | | stainless steel filter and non-toxic parts these |
| complicated. They use a drive shaft to raise and | | | | pumps are highly sanitary. They are resistant to |
| lower a flexible diaphragm with each stroke. This | | | | deposits of scale and rust. Diaphragm pumps will |
| changes the pressure inside the pump alternately | | | | not be damaged if it runs dry. |
| opening and closing an intake and outflow valve, | | | | Marcle Leisure can supply various pump |
| drawing water through. Diaphragm pumps require | | | | accessories such as additional filters, tubing, foot |
| more maintenance, are not usually submersible | | | | switches, non-return valves, expansion tanks |
| because water should not contact the mechanical | | | | (accumulators), and inline pressure switches. |
| parts. They are initially more expensive. | | | | Many 12 volt pump options are available from |
| Diaphragm pumps are self-priming. Certain | | | | Marcle Leisure for caravan, motorhome, and small |
| diaphragm pumps can handle dirty water and | | | | boat applications. By paying attention to the |
| even debris because the liquid does not flow | | | | various types and brands of pumps and their |
| through the moving parts. They can also maintain | | | | capabilities the owner of a recreational vehicle can |
| a steady pressure, however without an | | | | meet any need associated with the movement of |
| accumulator tank water flow can pulse. Also, | | | | liquids. |