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I've moved into a house that has one twin pump on the hot and cold water pipes (leading from the tanks) to make the upstairs shower more powerful. It works fine in the shower, as it switches itself on (mains electric) when it senses flow in the pipes as you first turn the shower tap on.

Unfortunately it also does this when it detects the flow of cold water to the bathroom taps and the toilets in the house. This means I'm paying money to fill up my toilets, and also means if anyone uses a tap in the night there is a loud whirring noise in my 3yr old daughter's bedroom cupboard. Not ideal!

I see there are two sensors which are fitted on the outside of the cold and hot water pipes into the pump. Shall I just unclip the sensor on the cold side, in order that demand for cold water doesn't start the pump up?

I think there is only one motor inside the pump, so a demand for hot water will trigger the hot sensor, and pump both hot and cold water. So the shower should still work the same.

Any drawbacks? Other than: the toilets will refill slower?

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2 Answers 2

up vote 3 down vote accepted

Disconnecting the cold water flow sensor certainly sounds like a reasonable idea. Try it and see if you get the desired result. Do use care when disconnecting as the sensor wiring may not be isolated low voltage circuitry.

When the pump is deactivated you will want to evaluate fully whether the upstairs toilets and sink faucet water flow is adequate when only cold water is used.

You also have the option to add in a timer circuit device that could cut off power to the pump motor during certain hours of the day/night. The timer could, if the proper type, simply be used to cut off the cold water sensor to the pump as opposed to just simply turning off the AC power to the pump motor.

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The only problem with disconnecting the cold water sensor is if your shower has a pressure balancing valve and there happen to be individual pumps for hot and cold. Based on your information this is not the case. Any valves installed in the last ten years should be pressure-balancing. As far as energy saving goes - this point load is likely never going to add up to more than pennies every month. As far as noise goes - it's quite likely that you can a) find a quieter pump or b) better sound-insulate the cupboard. This last is the cheapest and most efficacious from my distant viewpoint. –  Paul Dec 17 '12 at 14:41
    
Good idea to have a timer to keep things silent at night. That should be easy to fit. The pump is so damn loud that I don't think sound insualtion would work. Thanks everyone. –  MerlinMags Dec 18 '12 at 9:46
    
The pump manufacturer actually replied to an email (with a phone call) and advised that disconnecting one sensor wouldn't cause any problems. Hurrah! –  MerlinMags Dec 19 '12 at 15:31
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To answer the question in the title "Can disconnecting the cold switch on a shower pump save money?" The pump you linked to uses 345 watts. Assuming you use the cold water only in the bathroom for 10 minutes a day - cold tap, toilet flush, then you're looking at 5 hours per month at 345 watts. Call it 2 kilowatt hours. My local utility company charges about 15 cents per kilowatt hour. Your net savings will be $3/year.

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+1 for putting this into perspective. It's easy to get obsessed over a perceived energy inefficiency and ignore the real ones (insulation, lighting, behavior, ...). –  Henry Jackson Dec 17 '12 at 15:51
    
Heck! I should certainly stop worrying about the money then. Thanks. –  MerlinMags Dec 18 '12 at 9:44
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