Quietening caravan water pumps – easy and cheap to do

by Collyn Rivers

Most caravans and motorhomes use 12-volt pumps that have a rotating cam. This cam drives a flexible diaphragm up and down, typically feeding three separate chambers. These chambers draw water as the diaphragm moves downward and close as it moves upward. This action forces water outwards through further valves. Each chamber operates at about 60 times a second. Noise is created by various parts of the action.

Quietening caravan water pumps – how and where to start

The first step in quietening caravan water pumps is to ensure the pump has a truly rigid mounting. Knock on the existing or proposed base. If it sounds like a drum it’s going to worsen pump noise. Ideally have a truly rigid base, but if not place a small piece of carpet between the pump and its base.

The pump is normally attached via screws and small rubber mountings. Use the thinnest possible hold-down bolts that will adequately hold the pump (Shurflo recommend high-tensile 2.0 mm bolts) and tighten only just sufficiently to marginally compress the rubber mountings. Do not overtighten.

Flexible piping essential

Noise is also transmitted through the flexible hose connecting the pump to the various outlets. A surprisingly effective way of quietening caravan water pumps is to reduce this transmitted noise. This is readily done by having a full loop of truly flexible hose (never use rigid copper) between the pump outlet and the rest of the system. This loop should be allowed to hang as loosely as feasible – ideally in free space. Unless able to move freely a lot of noise will still be transmitted.

Avoid right angle elbow fittings. They cause turbulent water flow and back-pressure. Both generate noise. Use smooth curves instead. Another cause of the noise is the vibration of the piping and any fitting where the hose passes through a wall. Use soft plastic foam as an insulator. Plumbing can also vibrate against walls and drawers etc

Once installed, bleed all air from the system as any trapped air causes the hose to rattle.

Start off with one already quiet

A good solution is to start with a pump that is already very quiet – such as the Shurflo WhisperKing shown below – mounted as described above.

The Shurflo WhisperKing works as described above, but is a lot quieter than most such pumps. Pic: Shurflo

Another approach is to use one of the quiet (post-2010) constant flow pumps. These circulate unused water around an internal loop in the pump body. They are much quieter but draw up to twice the current of previous models. This not a major problem in an RV, but can be in (for example) an irrigation system that supplies low pressure to drip feeds over for long periods of time. Another more recent innovation is the variable speed pump. This seems likely to become increasingly popular.

Further information

This issue, and also a solution that provides totally silent operation nearly all the time, is described, in Caravan & Motorhome Electrics, Solar that Really Works!, and Solar Success. If you liked this article you will like my books. My other books are the Caravan & Motorhome Book and the Camper Trailer Book. All are written in the same plain English down to earth manner. They provide solutions that work.