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What is this fuse-protected electrical panel with on-off switch and indicator light? It bears the label MAINS WATER SUPPLY.

I have tried leaving it switched on or off for long periods of time (weeks or months) and can detect no effect either way.

The switch is in my UK kitchen on the 8th floor of a tower block. The building dates from 1965 but apparently had extensive renovation in the 90's. The kitchen certainly does not look out of date.

I have looked under the sink and at the back of cupboards but can find nothing electrical that it might connect to. The switch is in plain view above one of the work surfaces.

I asked a plumber - he had never seen one before.

I am mystified, can you help?

EDIT

I discovered that, on a quiet day, I can hear a faint humming sound when the switch is turned on. It sounds like an electric motor. However I can detect no difference in water flow.

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chasly - supports Monica
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    Is this an older house that at one time used a well pump for water, instead of city/town water supply? – crip659 Feb 28 '22 at 13:14
  • @crip659 - I'll add the info to my question. – chasly - supports Monica Feb 28 '22 at 13:17
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    The landlord/maintenance company/people should have all the electrical/plumbing plans for the building. They should have the answer. Might also be an electrical water shutoff valve(odd/rare) that has failed in the open position. – crip659 Feb 28 '22 at 13:30
  • is the fuse still good? if it's blown then it won't have any effect – ratchet freak Feb 28 '22 at 14:00
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    Pilot light should be after the fuse... – Ecnerwal Feb 28 '22 at 15:35
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    I'm going to say that someone on the 3rd floor has been _extremely_ irritated (and dirty) when you switched that off for months! – FreeMan Feb 28 '22 at 15:36
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    I was thinking possibly a booster pump on the 8th floor they may not have had good city water pressure and now they do and the pump was removed with the remodel in the 90’s. – Ed Beal Mar 01 '22 at 17:49
  • @Ed Beal - Hmm, that seems possible. I'll see if I can hear a pump when it's switched on. As you say, it may now be disconnected (although the light still comes on). – chasly - supports Monica Mar 03 '22 at 00:29
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    I would bet it was removed and the wires just capped, if you turn the switch off the water on watch the flow and turn the switch on and notice if there is an increase in flow. This would be 1 way to test. But since you did not notice anything with the previous test it may be capped. Checking with an amp clamp? But again if disconnected it won’t show a draw. – Ed Beal Mar 03 '22 at 01:53
  • I've added an update. I can hear a faint humming sound when the switch is turned on! – chasly - supports Monica Mar 13 '22 at 20:38

2 Answers2

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https://www.google.com/search?q=uk+"mains+water+supply"+switch produces results like:

It's a switch that controls a valve to turn off your water supply. Since the light still lights, power to the switch is still good. But since it doesn't cut off your water flow, probably the actuator has failed or possibly there is a wiring problem between the switch and the actuator.

nobody
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  • Yes, I found that linked device online. The problem is, it's non-electrical and operated by water-pressure alone. Quote "use nothing more than water pressure to isolate the incoming mains water supply (so no batteries or electricity)". My device is definitely mains-powered. – chasly - supports Monica Mar 03 '22 at 00:22
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Purely a guess, but perhaps something (a pipe heater) to keep it from freezing in cold weather. That might not be very obvious, depending on the type - for an "in the pipe" heater (the good ones) you'd have to spot the point where it entered the pipe.

Given the updated location, the "failed open electric water shutoff valve" mentioned in comments now seems more likely, perhaps.

Ecnerwal
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