Its true to say that certain types of jobs occur in batches. One week we will have a long run of draught proofing of sash windows, usually following a particularly cold weekend, and another we will seem to get a lot of shower repair requests. Last week it was shower pump repairs.
Modern shower pumps are designed to last for decades if they are installed correctly. Most manufacturers will offer lengthy warranty periods, but if the installer has not followed their installation guidelines religiously they will almost always wiggle their way out of replacing the pump under warranty. This is because even the best quality pump has an Achilles heal....air!
Shower pumps are designed to run continuously as long as there is a continuous supply of water. As soon as this water flow is interrupted by air the pump starts to misbehave. This misbehaviour can take the form of noise, vibration or the pump stopping all together.
So the first thing we check when we are called out to repair a shower pump is whether air has been drawn into the system. This is normally because the water supply pipe to the pump has been tee'd off the incorrect part of the hot water supply pipe and air is been drawn in from the expansion vent pipe. The answer is to create a dedicated water supply to the pump from the hot water cylinder. Depending on the pipe layout this can normally be done simply by adding a S Flange to the hot water cylinder. Which allows you to draw hot water from hot water cylinder without the risk of sucking air from the vent pipe.