Repairing the Watermill shower pump
One day my Watermill shower pump started cutting out.
It would run for a few seconds and then stop for a few seconds.
The strange thing was that it also did this when the shower tap was switched
off.
So I took it to bits and fixed it.
I found that one of the rectifier pack diodes had gone short circuit.
The reason it kept switching on and off was because the extra current passing
through the relay had made the contacts stick together.
There appears to be a safety thermal trip in the mains transformer and because
the transformer was getting hot the trip was repeatedly breaking and making.
The information here is just to help would be DIY fixers. I take no responsibility for anything you do.
Any risk associated with DIY fixing this unit is yours.
This faulty rectifier is the square block in the top left corner of the box.
I had a spare which is similar but a little too big to fit in the same location.
It looks like the faulty rectifier failed because the heatsink compound
underneath it had aged and become powdery causing the rectifier to over heat.
As a temporary measure I wired in the spare rectifier using a screw connecter
block. I used an old computer CPU heatsink for cooling. I drilled a hole
in the heatsink and attached the rectifier by screw. I used heatsink compound on
the CPU heatsink. It has been
working well for three weeks so I'll probably leave it like that.
To repair the stuck relay
I desoldered and removed the relay and levered the case off it. I was able to spring the
contacts apart and then clean them with some fine sand paper. The relay
case comes off easily so it might be possible to lever it off in place.
The two flow switches each contain a reed switch. They are worked by a
magnet that is inside a moving plastic float in the pipe. You can test the reed
switches by holding a magnet near them. I used a burglar alarm sensor
magnet.
The pump is about fifteen years old. Three of the original pipes have at
some time split at the pump and have been replaced by washing machine pipes.
These are more reliable because they are arranged so there is no strain caused
by sideways pull on the pump connecter.
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