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Earth wire under sink

  • 04-11-2023 7:47pm
    #1
    Registered Users Posts: 163 ✭✭


    I need to do a job on the kitchen sink and replace the tap. There's an earth wire under the sink located on the tap pipes. The earth wire will have to be rerouted to lower down. The new tap has flexihoses and not copper.


    Do I need to cut off the homes electicity when redirecting the earth wire?

    Post edited by Wearb on


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Comments

  • Registered Users Posts: 6,288 ✭✭✭10-10-20


    No, no need, just reinstall it on clean copper (brush it with sandpaper if it's corroded) further down.



  • Registered Users Posts: 3,472 ✭✭✭Shoog


    You need to make certain that the sink itself is earthed so use a link wire. The earth wire is there to ensure that if the sink goes live by say dropping an electric kettle into it, the circuit breaker on your ring main trips. The earth wire will be taken back to the nearest socket.

    The copper is probably already earth somewhere else in the house so it's essential you earth your sink.



  • Registered Users Posts: 206 ✭✭Bruthal.


    Interestingly, the kettle into a sink full of water very likely wouldn't trip the mcb. It probably would trip the rcd though, even if the sink is unearthed.



  • Registered Users Posts: 3,472 ✭✭✭Shoog


    That is what is intended and why we earth the sink.



  • Registered Users Posts: 206 ✭✭Bruthal.


    Sinks are "earthed" for equipotentiol bonding to keep all conductive parts in an installation at equal voltage should certain faults occur.

    The function of this bonding is not the same as the function of earthing in the kettle for example. The kettle earth is to help protect against faults in the kettle. The sink bonding is to help protect against faults in, or indeed outside the installation.

    There is a lot more to the field of earthing than "why we earth the sink"



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  • Registered Users Posts: 3,472 ✭✭✭Shoog


    The main check carried out on the sink will be to see if it trips the RCB in a simulated fault.



  • Registered Users Posts: 206 ✭✭Bruthal.


    They are bonded as extraneous metal parts. What tests are used to confirm the integrity doesn't alter that its a bonding connection, the function of which, is to ensure the equipotentiol status off all extraneous metal in the installation. That doesn't mean it won't cause trips in other scenarios such as a phase coming in contact with the metal sink etc. But the primary function is equipotentiol, and it might not be 0v. The main goal is all equal voltage in faults such as failed neutral in neutralized installations.

    Also, checking an item will trip an rcd doesn't really show its well earthed or bonded. An impedance of around 7k or under, phase to earth might trip one.

    If the sink was completely electrically isolated (plastic pipes etc), it can present more risk in fault conditions if it is in fact bonded, during some fault conditions. Nothing is perfect.

    My point about the kettle was just a matter of interest point. On another point of interest, sort of related to the kettle into sink full of water, I once introduced a phase conductor into the flow from a running tap into metal sink, via a multimeter in amps mode, and moved up toward the metal tap until the rcd tripped. Any guesses what the outcome was? It got a lot closer to the tap than would be assumed before 30ma was reached anyway.

    Post edited by Bruthal. on


  • Moderators, Motoring & Transport Moderators Posts: 6,515 Mod ✭✭✭✭Irish Steve


    Had to change a kitchen tap recently due to wear, so it's valid to point out that most taps are mounted on rubber or plastic washers, so it's important to make sure that there's still a good earth to both the sink and the tap itself, which can be made more complicated by the use of flexible pipe tails rather than copper, and the use of qualpex to provide the feed to the tap. Usually, the flexible tails have a wire mesh covering, so there's a way to get continuity across the tail pipe, but it's as well to check on completion that there is a good bond to earth from the tap as well as the body of the sink if it's metal.

    Shore, if it was easy, everybody would be doin it.😁



  • Registered Users Posts: 163 ✭✭MoonMotorway


    Should I be booking a plumber to do this work of changing a tap?


    It's so hard to get a plumber. 2 booked over the past month and they were no shows. I rang three more with no responses.


    I was going to change the tap myself and redirect the earth wire to the copper pipes lower down.


    It's so hard to get a plumber. There's now steam coming from under the lever of the tap even when it's not in use.


    This needs changing promptly. I have the tools and equipment ready to start the job.


    I was thinking I could try this job myself and redirect the earth wire and book a plumber and wait out the how many months it will take for a plumber to get to me and then they can take a look at the earth wire.


    Does every sink have and earth wire?

    I was doing some babysitting and I couldn't identify an earth wire in another person's home.



  • Registered Users Posts: 1,280 ✭✭✭Lenar3556


    Are metal sinks even earthed any more?

    I thought that was discontinued under current regulations?



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  • Registered Users Posts: 1,150 ✭✭✭monseiur


    You are overthinking this earth thing. Fit new tap, refit earth cable on lower copper pipe.....but before tightening ..... Get a few feet of 2.5 sq. earth cable, solder one end to base of sink and connect other end to refitted earth clamp on copper pipe.



  • Registered Users Posts: 163 ✭✭MoonMotorway


    Do I need to turn the power off to the home when working with an earth wire?



  • Registered Users Posts: 3,472 ✭✭✭Shoog


    Not really unless you need to take it back into the socket.



  • Registered Users Posts: 2,215 ✭✭✭deandean


    I got a bad shock a few years ago from my earthed sink. The washing machine developed a fault. I had my hand on the sink as I pulled the WM out and I got the full 230v up one arm and down the other. (The RCD didn't trip).

    In my case the sink is fed by plastic water pipes. I decided that I'd be a lot safer if the sink was not earthed, and I removed the earth connection.

    I don't know if this complies with the current regs, but I am safer without an earthed sink.



  • Registered Users Posts: 4,746 ✭✭✭Padre_Pio


    My sink definitely is not earthed.

    Taps and waste are plastic flexi pipes. No wires at all.



  • Registered Users Posts: 3,472 ✭✭✭Shoog


    This suggests you have a more serious earth fault somewhere.



  • Registered Users Posts: 193 ✭✭JL spark


    Yes , no longer done ,



  • Registered Users Posts: 1,914 ✭✭✭Andrea B.


    Are you saying you removed the earth bonding circuit from your sink to try mitigate against this?

    There are multiple potential reasons for you carrying a fault current (assuming +30mA) and it needs to be investigated.

    The circuit shock protection (assuming there) for the washing machine circuit did not work.

    Type AC or faulty RCD/RCBO, bypass of protection, no earthing on that supply, fault current you endured not long enough duration or high enough, etc...

    The next unfortunate instance may be a passage from that circuit through an individual to physical ground.



  • Registered Users Posts: 2,215 ✭✭✭deandean


    No my washing machine developed a fault. The t/stat failed and the water boiled for about 45 mins. It filled with steam and that's probably what caused an earth leakage but not enough to trip the RCD. No problem with the house wiring. I got the shock while pulling the appliance out with the other hand on the sink. I see no reason to have the sink earthed when it is fed with plastic water pipes, and it is staying that way.



  • Registered Users Posts: 3,472 ✭✭✭Shoog


    If you felt a shock then there is an issue, an RCD trips at about 40mA of current. I would not be happy if any current leakage fault didn't trip an RCD.



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  • Registered Users Posts: 1,280 ✭✭✭Lenar3556


    Typical RCD’s are designed to trip at 30mA - but much lower currents can still produce painful/serious shock.



  • Registered Users Posts: 1,914 ✭✭✭Andrea B.


    Honestly. How do you know your sink is not now earthed? It is likely incidentally earthed.

    Further, if it does not have good earthing, if for any fault reason the sink becomes live, then there may not be a path for fault current to spike to trip the circuit protection. So, leaving a live sink.

    If nothing wrong with your wiring (there is now, as you removed the sink earth), your RCD/RCBO could be faulty or not suitable spec. Unless of course you measured the fault current as below 30mA.

    Your washing machine is faulty.

    Honestly, your rationale around this is wrong. I think you know this anyhow.



  • Registered Users Posts: 1,280 ✭✭✭Lenar3556


    The issue was a faulty washing machine. The operator received a minor shock when pulling it out.

    An earthed sink could serve to worsen the impact of a shock in this situation as it provided a lower impedance path to earth directly through the body, as he was touching it at the same time.

    Sinks are no longer required to be earthed in current wiring regulations.



  • Registered Users Posts: 1,914 ✭✭✭Andrea B.


    The body of the machine became live. Fault.

    A current appears to have travelled through him from machine body to sink, which had an equipotential earth wire attached.

    Au contraire, for the OP shock instance, the sink being bonded should not have offered a lower impedance route through the OP, as the sink would have been equipotentially bonded to machine body (by the fact of sink and machine body being connected to the common earth circuit).



  • Registered Users Posts: 6,288 ✭✭✭10-10-20


    I wonder was it an oddity where a part within the washing machine, such as the drum, became live and didn't have a path to earth as it's a spring-suspended rotating part. Other than there being a fault on the earth off the socket or within the washing machine itself, that's the only way I can see this playing out as described.



  • Registered Users Posts: 1,914 ✭✭✭Andrea B.


    Agreed as possible root causes, but in my opinion, trying to turn the sink in to a "floating insulator" (OP assuming so by removal of bond connection)does not mitigate against the next fault scenario.

    Btw. Not trying to knock OP or other posters. Just trying to debate around the technical detail of what occurred and the OP's (and other posters) mitigation.



  • Registered Users Posts: 2,296 ✭✭✭Antenna


    One has to assume that the washing machine has an intermittent earth. This could be in the machine itself, the plug, the socket, or in an extension lead, if there was one used (I have, on more than one occasion, discovered disconnected or intermittent earths in extension leads . Its advisable to avoid using an extension lead anyway for something like a washing machine).

    And I have seen a socket with an intermittent earth (and not the fault of a loose wire/screw). Years ago I recall someone getting a small shock sensation opening a freezer with a metal handle, the socket earth was found to be intermittent, so whatever small leakage was felt rather than being directed to Earth.

    Moving the washing machine machine may have made the earth connection go open in any of the above. (Plug out before physically moving something like a washing machine as a precaution). It seems there was leakage, but not enough to trip RCD, however no shock should have been felt if the washing machine's earthing path was intact.

    Regarding the sink, I agree that earthing a sink connected by all plastic pipes (and not in contact with a metallic building frame) is introducing more serious possible danger than what it might remove.



  • Registered Users Posts: 4,959 ✭✭✭kirk.


    He only need to investigate the fault with the earthing/machine, not remove the bonding



  • Registered Users Posts: 1,914 ✭✭✭Andrea B.


    One doesn't have to assume anything. We don't know the facts outside of poster got a "bad shock" when touching both machine and sink.

    Further, on your last paragraph, can you elaborate as to how it could introduce more danger by having sink equipotentially bonded to the earthed machine in a compliantly wired scenario?

    Anyhow, removing earth wire from sink does not guarantee that sink is then insulated from earth. Poster may hope it is.

    Fundamentally, the machine is faulty though.

    Secondly, we can't say that the fault is above 30mA, but if it is, then there is a fault in the installation/protective device.



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  • Registered Users Posts: 4,959 ✭✭✭kirk.


    Below 25kohm(to MET) is the figure normally used to determine if a kitchen sink is extraneous and will introduce a earth potential afaik

    That's if you're testing which we don't do afaik



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