Shower Pump Running Dry

[GSD]

I recently replaced our twin impeller shower pump and being very concious of the fact that these mustn't be allowed to run dry I made quite sure that the power was turned off throughout the process.

However when I tested the new pump and found the hot water flow to the shower be rather low I thought that I ought to check that the new rubber washers on inlet and outlet to the pump were seated properly and weren't blocking the flexible hoses.

I therefore turned the water off and started to undo the the hose connection to the pump but forgot to turn the power off again. As a result the pump started to run for a very few seconds as the water pressure dropped before I was able to fully tighten the connection again.

Whilst the pump now seems to be performing as it should I would be grateful to know if I could have caused it any damage.

Many thanks, GSD

 

[Richard C]

You should always bleed pumps before switching the power on & testing. As to weather or not you’ve damaged the pump shaft seals, unlikely if the pump casing had some residual water inside; if it's not leaking at the moment (ceramic seals will usually show sings of damage immediately) who knows, only time & use will tell. Use & enjoy.

 

[GSD]

Thanks very much for getting back to me so quickly and, as instructed by the pump manufacturer, I did allow water to run through the pump by gravity for a few minutes so as to expel any air before switching the power on again. I can't detect any leaks from the pump at the moment so hopefully everything will be alright.

However I had thought that any damage would be to the impeller bearings rather than the shaft seals so I would be interested to know if these are sealed units which may or may not be cooled by water, or whether water lubricates them in some way.

With many thanks again, GSD.

 

[Richard C]

The bearings fitted to shower pump motors are conventional mechanical sealed for life bearings units running in pre pre-packed lubrication, they are not the same as ceramic water cooled bearings you will find in submersible (pond) pumps. The pump impeller casings have ceramic end seals & it’s these that need water lubrication to prevent damage, just like a neoprene or rubber seal; ceramics are pretty tough though & need serious overheating before damage will occur. If your pump previously had water in the impeller housing, it would need to run considerable longer than a few seconds before the seal ran dry, overheated & damage occurred; residual water in the housing would still provide enough lubrication/cooling for several minutes or more.

 

[GSD]

Richard C, thanks very much indeed for this which which is very reassuring. With best wishes, GSD.