Q Why is my water pump excessively noisy?

I have a 2022 Compass CV40 campervan and, when using the on-board water pump, it makes an excessive noise, like a machine gun. Other ’vans we have had made a low hum but this noise is driving us mad.

The pump is on rubber mounts, we have tried to use rubber between any close woodwork and have insulted the pipes where we can see them. Any ideas how to minimise further?

Gary Chapman

A From your description of the pump on rubber mounts I assume it is of the type that responds to water pressure. Several ideas for you to look at.

There could be a loose electrical connection to the pump as each time the pump starts it moves on its mounts and temporarily disconnects its 12V supply. As soon as it stops the pump moves back and the connections remake and that is how it continues. Check all the immediate and any nearby connections for cleanliness and tightness.

Another option is that these pumps include a switch that disconnects the 12V supply once the water pressure at the outlet exceeds a preset level. You open a tap, the stored pressure drops and the pump starts.

If the tap is fully open the pump continues to run. If the tap is partially open the pump cycles on and off sufficiently to maintain the outlet pressure. Close the tap and the pump stops once the pressure is built up in your plumbing.

This can result in frequent on-off operation of the pump and many installations include a surge damper in the plumbing system to reduce the on-off frequency. The surge damper is effectively an upside-down plastic bottle with the only outlet positioned at the bottom, this outlet being tee’d into the pump’s outgoing water feed.

When the pump runs and the tap is not fully open, water will run into the surge damper, compressing the air above the water. Eventually the water and air pressure inside the damper will reach the switch cut-off pressure and the pump will stop. Water then continues to flow coming from inside the surge damper and pushed out by the air compressed above it. Once the pressure has fallen below the switch-on pressure, the pump will start again.

Problems here can be the plastic retaining clip for the surge damper has broken and the damper is laid on its side. The air comes out, it fills with water and becomes ineffective. In my case a small pin hole in the surge damper allowed all the air to escape and frequent on-off of the pump was the result. The growing puddle on the floor pointed to where we needed to look.

Clive Mott