I can't say I've ever tried, or had the need. I imagine that it would be possible, but a bit of a performance to either take it apart and soak the components, or find a way of filling the pump with the fluid. I do wonder why yours has failed, if it really is due to limescale. Put it this way, my own shower pump is somewhere between 25 and 30 years old, and in a hard water area ! It just might be a good idea to check that the makers installation instructions have been followed to the letter.
All I can say is that limescale was the reason given for replacing the pump. The shower had not been switched on for a time and when it was you just heard the motor whirring away but not kicking in. Consequently the shower head just dribbled. If left on too long, a smell of hot components could be detected and the pump itself was very hot to the touch. It had worked fine for about four years and I too live in a hard water area.
When the pump is detached there are the four pipe holes. I was wondering whether you could use something like the stuff you use to descale kettles, preparing it and then pouring it in.
But you could be right, it may not have been caused by limescale at all. I suspect if it was just the motor, it is easier to replace the whole pump or perhaps not even possible to buy the motor separately.
I just wanted to update this thread. I did pour descaler into the shower pump and left it for a time. I can't say I noticed any deposit as I emptied ithe fluid out. Anyway I reconnected the pump and it worked fine. Whether it was the descaler or just moving the pump as I uninstalled/installed it I don't know - but the pumps cost over £200 new so it's worth a try every time.
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