Using half a shower pump

[Tim Downie]

I'm currently looking for a pump to boost the HW pressure downstairs and things being what they are, it's probably going to be bought on ebay.

The thing is, there are many more twin impeller pumps to choose from than single impeller pumps. So, my question is, does it damage a pump to only use one side? Most twin impeller pumps seem to be identical to their single impeller cousins (apart from the extra pump chamber) but of course there my be differences in the bearings.

If it's not good to use just one side, I don't suppose there's anything wrong with pairing up the inlets and outlets is there?

Tim

[John Rumm]

That would be my preference. Saves running one side dry.

[Andrew Gabriel]

I suspect you'd end up with smoke from the dry side.

I guess you could double up to increase the flow, or run them in series to increase the pressure.

[Arfa Daily]

All of the twin impeller pumps that I've owned over the years, specifically warned against running the pump with the chambers dry.

Arfa

[Bob Mannix]

The bearings (usually) require water. Running a twin impeller pump with one side dry would (probably) seize the dry side and put unbalanced wear forces on the shaft anyway.

Doubling up in series probably wouldn't gain you much pressure and might cause some vibration/noise modes depending on the dynamics of the flow/pressure. Paradoxically, you would get a better perceived pressure gain by running both sides in parallel as, although the hydrostatic pressure would be the same, the pressure drop with flow would be reduced, leading to a better pressure in use (IMHO), and everything would be balanced. Having said this, at low flows there will be a lot of turbulence from the impellers driving over capacity, which *might* increase the noise. If you have to have a twin impeller, run both sides in prallel is the answer!

[Tim Downie]

Thanks all for the replies. Didn't win the pump I was hoping for but will keep looking.

Tim

[YAPH]

If you're in the Reading area I've a 2 year old bog standard twin impeller shower pump I've just taken out of a job (put in a mains pressure HW supply). A brown beer token secures :-)

OTOH if you want a really good pump for not outrageous dosh you can't do much better than the Salamanders that Screwfix do for 100 notes.