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In my home, we have a recurrent problem with certain water outlets becoming electrically LIVE enough to give a slight shock when touched. In particular this happens to a shower, but it is not limited to this location.

I've had 2 electricians look at it in the past. One found a faulty socket and repaired it, the other ran some extra earthing wires which seemed to solve it - or at least greatly reduce it - but it has come back again.

The symptoms are: 1) slight shock when touching the shower valve once the floor is wet, 2) multimeter set to DC shows voltage of around 0.2 volts between the valve and my hand when I'm standing on the wet floor. On AC setting, I get no reading at all.

So, it's one thing to run some extra earthing to stop the problem, but 1) What could be causing the pipework to become Live in the first place? 2) Why is the existing earthing inadequate?, 3) Why is it direct current rather than alternating?

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  • Comments are not for extended discussion; this conversation has been moved to chat.
    – BMitch
    Sep 5, 2022 at 14:12

8 Answers 8

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The most probable cause of this dangerous problem is a failing electric+plumbing appliance, such as a clothes washer, dishwasher, or electric water heater.

The casing of the appliance, which is properly grounded, has become energized via some short-circuit or other failure that is -- so far -- allowing only a small current to flow. This will change when the failure becomes worse.

If you're lucky, the failure will get worse and the increased current will trip a circuit breaker. If you're unlucky, your shower will kill you.

To diagnose the problem, use a contact voltmeter to measure the potential difference between your shower and a good reference ground (such as the ground bar in your service panel). I usually do this with the aid of a long extension cord.

Turn off circuit breakers until the shocking voltage on your plumbing goes to zero. The appliance on the suspect breaker is the likely culprit.

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  • Thank you - my feeling is it must be a power/water interface somewhere too, but 1) the dishwasher has been replaced TWICE since it started, 2) The water connection for dishwasher and washing machine are both plastic flexible pipes, 3) the voltage is there even with the electric water heater switched off. The water softener would have been a great candidate because it runs on 12v DC or thereabouts - but switching that off didn't solve the problem either! First stage is to switch off circuits until the voltage disappears (see my other comment). Luckily there is RCD protection on the whole panel.
    – Lefty
    Sep 4, 2022 at 9:21
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    @Lefty In the past, it was legal at one point for copper water pipes to pull double duty as the ground conductor. So, the offending appliance might not be one that uses water, it may be just plugged in to an outlet that's grounded via the plumbing. Sep 4, 2022 at 15:40
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    " At one point, my main water pipe was converted from Lead to Plastic..." - See, some details are more important then others. Sep 4, 2022 at 16:46
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    @Lefty "I believe that they did something to give me a new Earth connection." You might want to check that, because the fact that you're getting shocked by your fixtures might indicate that at least one outlet/circuit/whatever might still be connected to the plumbing. Sep 4, 2022 at 17:09
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    Yes, that is exactly what I think is happening. Also, now that I know that there are Earth wires connected to the plumbing in multiple places throughout the house, I think that the electrical current leak could be at anywhere, not just at a major electric+plumbing appliance. Sep 4, 2022 at 18:15
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Three things:

  1. You may have inadequate grounding (earthing, you must not be in the USA!)
  2. You have a serious ground fault somewhere.
  3. You may have a weak/bad neutral connection to the power mains.

Does everything else work as expected? Any unusual dimming of lights or excessive brightness?

Here in the USA hot and cold water pipes, if they are metal, must be connected to the grounding bar in the main panel and 2 ground rods must be installed and connected as well.

I suspect a ground fault in your water heater, but the fault could be anywhere.

To diagnose, it would be best to use a meter rather than a human to find the fault. If the voltage changes as the person at the panel is turning off circuits then you'll know which circuit is causing the fault. If not no changes, there might be a weak neutral connection, allowing current to go thru ground connections.

If you have access to an "amp clamp" style meter and the wires going to the ground rod, it would interesting to see if there is any current flowing there and how much.

Telling us where you live on this blue orb will help give better advice.

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    I really must protest this method of using a wet human as a wattmeter. What if the person at the panel does something that changes this 0.2V problem into a 120V * 15A problem? - Please stay away from this lethally dangerous plumbing until the problem is corrected! Sep 3, 2022 at 22:02
  • That's a good comment. Probably best to use a meter rather than a human. I only said what I said bc the problem seemed so mild, but ur right, it could get worse. I doubt thou that a ground fault would trip a breaker, it'd have to be a really really bad one. Still. I'll update my answer based on your comment. Thanks. Sep 4, 2022 at 0:37
  • I am in the UK, so yes, it is "earthed", rather than "grounded" and we have 240 Volts. The water is mains fed through a plastic pipe and the entire system is mains pressure. It's a gas boiler heating the water in a cylinder, and there's an immersion heater for when the boiler stops working - but it is currently OFF. As it happens, the boiler has recently been replaced - and the circulatory pump is built-in to the boiler so I doubt that is faulty - and the problem was unchanged by swapping the boiler.
    – Lefty
    Sep 4, 2022 at 9:09
  • The idea of switching off circuits was not one that occurred to me, so thank you, I will definitely be using that method to isolate it. For complicated reasons turning off the power is not something I do lightly, but I will do it as soon as I am able.
    – Lefty
    Sep 4, 2022 at 9:12
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    Yeah for some reason in the UK we use "earth" in electrics and "ground" in electronics. "The audio ground is connected to the mains earth" would be a valid sentence.
    – Rodney
    Sep 4, 2022 at 10:22
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I am in the UK and have experienced this exact problem. Cause was as follows:

  • Many older UK houses do NOT have any form of ground\earthing conductor coming into the property, and there is NO earth-neutral bond in the meter cupboard. All "earth" cables in sockets were bonded back to the lead water pipe.
  • The plumber removed the lead water pipe and replaced with plastic. This removed all connections to actual earth under the house.
  • The green & yellow wires in the the house that were previously connected to the water pipe in the meter cupboard, run alongside the live wires in the rest of the house. They could now "float" up towards the mains voltage due to induction. The metal cases of all switches, appliances etc now also had this high floating voltage on them, enough to cause a painful shock.
  • Once we got an electrician in who discovered what the plumber had done, he re-instated the earth and we no longer got shocked by light covers, the kettle casing etc
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    This is really interesting because it sounds like exactly what might have happened to us. Particularly since I can't begin to imagine what appliance might be leaking to earth, given that they've all been replaced since this started! I think I'm going to work on the assumption that this is the closest explanation, and see if I can investigate whether I have an earth or not!
    – Lefty
    Sep 4, 2022 at 21:59
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    Note that if you're in the UK, the DNO (the electricity network - not the supplier you pay your bills to) has a responsibility to provide an earth to your home, read this page: ukpowernetworks.co.uk/electricity/earthing
    – Ralph
    Sep 5, 2022 at 7:27
  • That's really good information, thank you.
    – Lefty
    Sep 5, 2022 at 7:56
  • @Lefty Every piece of electronic equipment with an earth lead has a capacitor from live to earth and from neutral to earth for interference suppression. If your earth system is floating, the impedance of the capacitor is low enough to give you a tingle and (in the UK) you can measure 120 V AC with a digital multimeter on the earth wire. Bonding of exposed water pipes to earth in bathrooms and at the boiler was only required from about 1980.
    – grahamj42
    Sep 5, 2022 at 11:16
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Just to offer a more simple diagnostic, try turning off the main disconnect for the dwelling electricity. This will help to determine if the shock potential is coming from the electrical system or not.

In one of the comments you mentioned probing the drain. This can be unreliable because there is no way to know if the drain is grounded. Many sewer pipes are plastic or ceramic. Consider using a length of wire to connect your multi-tester to the ground contact in the closest receptacle.

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  • It is odd that the drain acts as a connection - the cover itself is metal - but I am 99% certain it is plastic from there - and it goes into a hopper rather than into the ground, so I don't understand how this is electrically connected to ANYTHING. All I can say is that when I touch the multimeter to the shower valve, I get zero volts until I touch the drain cover with the other probe.
    – Lefty
    Sep 4, 2022 at 8:56
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    @Lefty Reading 0.2V off some random object is not odd. That is normal. Sep 4, 2022 at 12:13
  • Fair enough - but it is normal for me to get a regular (albeit small) shock by touching a shower valve?
    – Lefty
    Sep 4, 2022 at 16:25
  • @Lefty No, and 0.2V wouldn't cause a shock, even if you licked it (don't lick your shower valve)
    – user253751
    Sep 5, 2022 at 13:09
  • @user253751 The point I was trying to make is that I get a shock from the plumbing - and that I measure a NON-ZERO voltage between the valve and the drain (which shouldn't even really be earthed as far as I'm concerned). Many people have focussed on the 0.2 Volts - but I have no faith in this as being an accurate measurement of the voltage that is giving me a shock. Contrary to suggestions here, I can measure random things all over the house and get zero volts, even my own body. Perhaps everyone else has a better AVO than me because I don't see random 0.2 volts anywhere else.
    – Lefty
    Sep 5, 2022 at 19:13
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Many years ago I lived in a student residence where people were shocked by the shower when the floor was wet. Multiple tests showed the shower was well earthed. Fully investigated only when a person was hospitalised.

Long story short, the shower was well earthed. Trunking under the floor was not, when wet the floor was live. Standing on the floor and touching the shower gave a shock.

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  • I don't think this is likely in my case - but worth mentioning here for completeness, thank you. I am quite aware of where my wiring goes and I would be surprised if any mains wiring was under this bathroom. Also, the floor is VERY well waterproofed and it is relatively new.
    – Lefty
    Sep 5, 2022 at 8:08
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This used to be an artifact of an electricity stealing when the old, mechanical electric meters and steel, electrically conductive water pipes were used.

How it was done:

  1. Disconnect the neutral from the meter at both the utility side and the house side. Bonus if you can do it both invisibly and reversibly.
  2. Use the water pipe as a neutral
  3. Optionally, connect a resistor between the newly established "neutral" and the neutral going to the meter. The meter will run, but at a reduced rate.

The problem was, the water pipe is not very good as a neutral. 20-30V (in a 230V environment) between the "real" ground and the false neutral were pretty much expected. This is how one got refreshing shocks from the plumbing.

You also got the same shock when you didn't steal electricity, but your neighbor did.


What you experience now is that you either have a "lost neutral" connection between the utility and your home (Harper, where you are?) or a grave ground fault in some water + electricity appliance.

Again, it may be your neighbor having one of these.

How to debug:

  1. Get a proper ground. Failing everything else, a metal rod in the soil will do. Insert at least half a meter in a moist soil. Make it moist if it isn't (you will need the whole construct temporarily).

  2. Connect the voltmeter between the offending faucet and this new ground. You may need an additional wire.

  3. Test by switching everything on and off, including the main breaker.

... or get an electrician that knows what they are doing!

Good luck.

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It's possible the new switch fitted has gone bad. It happens.

Using a multimeter, set to volts, check the taps for voltage by putting the negative terminal to the tap and put the positive terminal into the water and you'll get a voltage reading. Obviously this is not how it should be but it's a way to confirm the problem.

Go-to your fuse box and find the circuit for the shower and turn it off. Redo the above test. If you don't have voltage (hopefully) check inside the switch for visible signs of burning/heat damage. Assuming you find some damage you'll need a new switch. (We had a switch replaced and the electrician joined two live wires together that must have been arching, which eventually killed the switch again).

If it's not the switch it will more than likely be another water/electric connected item like a boiler or electric water heater (under sink one).

A good electrician should be able to find a fault like this fast. Just make sure thier work has a guarantee.

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  • Hi, there has been no "New switch fitted", the shower is not electric.
    – Lefty
    Sep 4, 2022 at 16:23
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Could I simply put a copper strapping on the cold water pipe and attach it to a copper peg in the ground? Will that prevent me coming alive when the geyser is on and I am taking a shower. It only happens to the cold water tap

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  • Hi Gary, this site works differently. You have asked a question in the answer box. Please ask it in the question box. Dec 3, 2023 at 10:44

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