As per title, recently the shower pump is playing up

– sometimes takes up to 30seconds to kick in
– sometimes isn’t kicking in at all
– seems to kick in fastest when is at either max. hot or max. cold

Not really sure where to start – the fact that sometimes (within the same hour) it’s fine says to me the pump is fine and it’s something else? Water pressure is constant. The pump is a Poterton Myson with 4 inlets/outlets.

One or both of the microswitches that detect flow playing up would be my guess. I can’t see a Potterton Myson shower pump anywhere online, are you sure that’s what it is?

correction! it’s a Myson Aquaboost

Pressure switch scaled up limescale possibly, or other such debris.

Could be more terminal, internal corrosion or leaking into electrics – without inspecting you won’t know.

I had a similar issue and ended up just putting a new one in, was going to be easier than messing around trying to descale it. Bonus is the new one (same make and output) was much quieter.

From about £130 quid from screwfix…

J

Are the microswitches housed within the pump OR are they the black boxes (also Myson – code FSVR-3) that run inline on 2 of the pipes and have a powersource to them?

I know a man, ehm, whos shower had no water coming out at all. Thought the pump had gone so replaced it. Still no water. Then realised there was a kink in the shower hose that stopped the water coming out.

Are the microswitches housed within the pump OR are they the black boxes (also Myson – code FSVR-3) that run inline on 2 of the pipes and have a powersource to them?

IANAP and can’t say for sure but almost certainly in the black boxes if there is one each on H&C and there’s a pair of wires. When it refuses to run does giving the black boxes a tap let it start? Which would point to a stuck float/faulty reed/however the switch works. I still can’t see much on Myson Aquaboost online so I’m guessing it’s old and out of production and spares might be hard to come by. As long as you’re sure your water pressure is OK your best bet might be the ffej route of replacing the pump, it’s an easy job. Worth checking first it’s not something daft like scaling on the shower head or a lump of gunk somewhere in the works though.

Assuming this is a shower pump that up has worked well for a long time until now? Assume this is a gravity system?
And I assume there’s a bar mixer shower.
With that said, first things to check are:
1. The pump relies on detecting a reasonable flow of water to kick in. So any scale build up that prevents flow could prevent it turning on. mixer showers commonly have little mesh filters on the inlet designed to catch crud, which scale up. Remove mixer from fittings and inspect/clean.
2. Pump likely to have mesh filters also on inlets, dismantle and inspect/clean.
3. Micro switches as above.

Update: there’s a rigid black plastic box on top of the pump which has electrical connections – when the pump fails to kick-in a small smack on top of the box makes it start up. No idea what this part is or why a smack makes it work – anyone know?

Could it not just be air in the system? From recollection, turn the power off, turn the water on then off to empty the pump and loosen pipes to bleed, then you can turn pump on again. Gotta be worth a try.