Noisy shower pump in dead of night
February 8, 2009 10:52 PM   Subscribe

Why is my shower pump suddenly starting up when the shower is off but hot water is used elsewhere? Can it be stopped?

The pump was installed about 18 months ago when we had a shower room added. It's in the airing cupboard with the hot water tank. It was always noisy, but worked fine. Lately I've been hearing it start up for just a second when hot taps are turned on and off, which seemed odd but wasn't a problem. Then yesterday we had our kitchen sink and taps replaced, and using the hot tap afterwards I could hear the shower pump pulsing on and off very quickly. I got it to stop by turning the tap on and off again and hoped the problem would sort itself out. Then at 3am the washing machine turned itself on and the shower pump began to pulse, waking us up. It's never responded to the washing machine before, but of course the attachments all had to be taken off and replaced when the sink was changed, so something must be different.
The worrying thing is my neighbour seems to be an insomniac and had already complained about my running the washing machine at night. (Which I have to do as my electricity is Economy 7.) I expect an irate visit as soon as the sun comes up, especially as the noise started up again a second time when I thought I had turned the shower pump off and restarted the washing machine. A thick white wire runs from the pump to a switch and fuse, still in the airing cupboard, labelled 'heating and hot water'. When I turned it off the clock display for my timed central heating went out and I assumed the shower pump would be off too, but it managed to run anyway. I can't see any other switch that might turn it off, or any other electrical supply attached to it.
Googling for problems with shower pumps has suggested that the pulsing on and off problem could be due to the boiler heating the water too much (though it is already set at 60 Celsius) or to air in the pipes, but why is it coming on at all when the shower is not on?

I'd be very grateful for any advice. I don't dare turn the washing machine on until my neighbour has gone to work now, and the same may happen with the taps - I don't dare to try them either yet! More details in case they help: there is an electric immersion heater for water but it is not used and is switched off (switch outside the airing cupboard), the washing machine has red and blue hoses attached to hot and cold pipes under the kitchen sink, the water is heated by gas from a back boiler which I have checked yearly - most recently only a couple of weeks ago - the central heating is through radiators, it's a semi-detached house so I only have the one neighbour to worry about but she's very bad tempered, I'm in England, and the pump has 'Wickes Twin Impeller' written on it. Thank you for reading, sorry about the length.
posted by tulipwool to Home & Garden (3 answers total)
It's probably designed to turn on when the pressure drops. Turning on hot water faucets elsewhere in the house will cause that.

So it runs, for just a moment, and because the tap on the far side of it isn't open, the pressure builds up rapidly, and it turns itself back off again.

Just as a guess, it could probably be tuned to be a bit less sensitive to pressure drops, and would cease responding that way. But the folks who installed that pump would really be the ones to ask.
posted by Chocolate Pickle at 11:44 PM on February 8, 2009

Chocolate Pickle offers good advice.

I've done some reading on UK shower pumps, and it appears to be an adaptation to
low supply rates. There is no auxiliary tank installed (often called a "captive air" tank in
the US), so your shower pump cannot increase the water flow (much). It can simply
increase pressure, as long as the rate of flow is about the same as what it would be
without the pump.

That said, your entire hot water system is probably downstream of the shower pump.
At the time of installation of the shower pump, it probably took a minimum decrease in
water pressure on the demand side to turn on the shower pump. This setting was
probably calibrated at the time of installation.

If the pressure in your supply line has decreased since installation of your shower pump,
or if the flow rate has decreased, then it might produce the behaviour you describe in your
shower pump. It's threshhold for "on" might need to be reset so that it responds properly
to the reduce pressure or reduced supply rate of your water line.

If your new taps allow more water to flow per second than the old taps, the shower pump
might show the same behavior. If you have "stop valves" (just upstream of your taps,
which allow you to service the taps without shutting off the suppy for the entire house),
you might consider closing them a little, to reproduce the flow rate of the old taps.

The shower pump might have a pressure switch on it that can be turned on or off. If you
are doing laundry, you do not need the shower pump, as your washing machine operates
on a volume basis, not a pressure/time basis.

Long distance plumbing is always risky, so let your own observations guide you before
taking advice from a handy home plumber in another country.
posted by the Real Dan at 12:13 AM on February 9, 2009

i know my washing machine has an integrated water heater. it has both cold and hot inlets, but i only have the cold water inlet connected and if a warm cycle is chosen the washing machine heats the water itself.

i have no idea how common this is in washing machines but you could try running yours from only the cold inlet and see how it goes.
posted by onya at 1:12 AM on February 9, 2009

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