Power Shower Pump Cavitation.

[CatSailor]

We've recently moved into a bungalow which had an existing power shower pump fitted in the airing cupboard and supplied the shower in the bathroom.

When we first moved in in October the shower performance was OK.

However, as the weather has got progressively colder and with it the cold water fed to the shower which therefore required an increase in hot water flow, so the hot side of the pump has started to cavitate quite badly.

I've done a bit of searching on this forum to try and establish a way to rectify this but the pump does appear to be more or less correctly installed.

The hot feed to the pump is in 15mm via what looks to me like an Essex flange mounted 8-10 inches down from the top of the cylinder.

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• CatSailor
• 8 Feb 2009
• 2

I have measured the temperature of the hot water feed at the kitchen tap and that is 55deg C.

The hot and cold inlet and outlet to the pump are fitted with what I would call 'washing machine' service valves, but I'm not sure if they cause any restriction.

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• CatSailor
• 8 Feb 2009
• 2

I'm not sure where/what I should do next so any sugestions welcome.

Thanks

Adrian

 

[Dan Robinson]

It is a cheap and nasty pump, so it could simply be the bearings wearing out.

 

[Richard C]

“Cheap & nasty pump” it maybe, I won't comment but if it is the bearings, they will let it be known & the pump will be very noisy. I don’t really see how that will cause cavitaion though, for that you need air getting in the system somewhere!

First thing to check; looking at your pics, the pump seems to be installed above the H/W cylinder; you have an anti-gravity loop but I can’t know where the rest of the pipe work is going. In an up & over installation, you should have an open vent at the top of the loop before the pipe dives back down to the shower otherwise air will accumulate in the top of the loop; your pump will constantly be sucking aerated water & as the air (& pressure) builds, it will eventually stop drawing water altogether! This also applies to the cold feed loop (if it’s the same) but it will be less noticeable as cold water doesn’t liberate so much air (oxygen).

The pump inlets usually have mesh filters, have you checked & cleaned them out? Can’t see from the pic but are you sure it really is an “Essex” flange & not just a tank connector with an elbow on it? Your correct about the washing machine valves, they will severely restrict flow, "full flow valves” should be fitted but, as you can probably guess, they aren’t cheap. You can get them “on line” at a fraction of the price you local “Plumb Centre” will rob you of; it’s also a shame it’s only 15mm feeed, 22mm is really necessary for a serious power shower!

There’s a few things to check come back if you need more.