Power Shower Pump Noisy or Pulsing

What's happening?

A shower pump boosts a gravity-fed hot and cold supply so a shower has flow. It runs while the shower is on and stops when it is off. Some noise is normal, and manufacturers say so. A change is the signal: a louder or grinding pump, one that pulses, or one that starts and stops while the shower is running. Stuart Turner, a pump maker, says pulsing during use is often caused by a blockage such as a scaled head or a collapsing hose that creates back pressure, and that the flow to the pump should be at least 1 litre a minute. Mira says all pumps make some noise, that installation conditions can amplify it, and that on an existing installation the pump motor may be faulty.

What usually causes it?

• A scaled shower head or a kinked or collapsing hose raising back pressure
• Too little water arriving, from a low tank, a part-closed valve or a blocked inlet filter
• Air in the pump or the pipes, which makes it cavitate and rattle
• A pump mounted on a hard surface so its vibration carries to the floor and pipes
• A worn pump motor or bearings growling or squealing
• A pump that is not sized for the shower or pipes
• A hot supply that bounces back through the pump when the outlet is off

Is it dangerous?

Low. A pump that runs dry or is made to work against a blocked outlet can overheat and fail, so stop using it if it is grinding or hot. The pump is on mains electricity: switch it off at its isolator before touching it, and leave the pump body closed.

Can I fix it myself?

Run the shower with the head off, then with the hose off, to find whether the pulsing comes from the head or hose; descale the head in vinegar and replace a hose that collapses. Check that the cold tank is full and that any inlet valves and filters on the pump are fully open and clear. An anti-vibration mounting pad under the pump reduces noise carried into the floor. Do not open the pump casing. Check the maker's guide to see whether the noise is normal for the model, and whether the pump is still under warranty.

When should you call a plumber?

Call a plumber when cleaning the head and hose has not helped, when the pump is grinding, hot or leaking, when the flow arriving seems too weak, or when the pump is in a loft or airing cupboard and cannot be reached safely.

What will the plumber actually do?

• Check flow and pressure into and out of the pump, and the state of the head, hose and filters
• Bleed air from the pump and the pipework and check the inlet supply
• Fit an anti-vibration pad, flexible connectors and clips to stop noise carrying
• Add a non-return valve on the hot outlet where the supply bounces
• Repair or replace the pump, or resize it to the shower and pipework

Who fixes this

• Shower pump installation
• Tap and shower repair

Questions people ask

Sources & References

1. Stuart Turner: shower pump frequently asked questions
2. Mira: why is my shower pump making more noise than usual
3. Mira: my pump is noisier than usual