Earth wire under sink

MoonMotorway

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?

10-10-20

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

https://www.boards.ie/discussion/2058321087/earth-wire-under-sink

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.

Bruthal.

https://www.boards.ie/discussion/comment/121326028#Comment_121326028

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.

https://www.boards.ie/discussion/comment/121326752#Comment_121326752

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

Bruthal.

https://www.boards.ie/discussion/comment/121326856#Comment_121326856

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"

https://www.boards.ie/discussion/comment/121326918#Comment_121326918

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

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.

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.

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.

Lenar3556

Are metal sinks even earthed any more?

I thought that was discontinued under current regulations?

monseiur

https://www.boards.ie/discussion/comment/121327452#Comment_121327452

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.

MoonMotorway

https://www.boards.ie/discussion/comment/121329401#Comment_121329401

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

https://www.boards.ie/discussion/comment/121329526#Comment_121329526

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

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.

Padre_Pio

My sink definitely is not earthed.

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

https://www.boards.ie/discussion/comment/121330262#Comment_121330262

This suggests you have a more serious earth fault somewhere.

JL spark

Yes , no longer done ,

Andrea B.

https://www.boards.ie/discussion/comment/121330262#Comment_121330262

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.

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.

https://www.boards.ie/discussion/comment/121394023#Comment_121394023

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.

Lenar3556

https://www.boards.ie/discussion/comment/121394070#Comment_121394070

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

Andrea B.

https://www.boards.ie/discussion/comment/121394023#Comment_121394023

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.

Lenar3556

https://www.boards.ie/discussion/comment/121402444#Comment_121402444

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.

Andrea B.

https://www.boards.ie/discussion/comment/121415617#Comment_121415617

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).

10-10-20

https://www.boards.ie/discussion/comment/121415774#Comment_121415774

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.

Andrea B.

https://www.boards.ie/discussion/comment/121415832#Comment_121415832

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.

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.

kirk.

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

Andrea B.

https://www.boards.ie/discussion/comment/121417445#Comment_121417445

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.

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

Bruthal.

https://www.boards.ie/discussion/comment/121418415#Comment_121418415

I think the poster is saying that bonding a sink can introduce more risk than not bonding.

In this particular case, it would have been less likely to receive as severe a shock with the second hand in contact with isolated metal than earthed metal.

But the sink bonding is to mitigate against potential differences in installation fault conditions, or faults outside it (failed neutral at minipillar etc). Bonding the sink can increase the risk compared to an electrically isolated one. That risk was seen in this case also.

kirk.

Mostly there shouldn't be a hazard. There's bonded metalwork everywhere in installations.

It's happened a fair bit with plumbers in hotpresses getting electrocuted . A spark would be more aware of the risks and take precautions

Andrea B.

https://www.boards.ie/discussion/comment/121422742#Comment_121422742

We have nothing to confirm that this sink without bonding connection has a high enough resistance to prevent a fatal current. It may or may not.

If sink, incidentally has a high enough resistance, then there is nothing to say that the floor to human contact will not be the route for the fault current in the next instance.

Fundamentals are, a faulty machine and if it is a +30mA fault not tripping RCD, it starts to point towards something not conforming with wiring or associated protection.

Further, the bonding that existed before the wire removal, should have been the least resistance fault route to allow equipotential state of live machine body to sink, so, something (seems) not equipotential there if a shock level current travelled through poster.

If hand to hand is approx 2.3kohm, and the equipotential bond of sink to machine 1ohm, then for a 30mA (assuming RCD would have activated otherwise) fault current using the bonding route, the human coming in parallel would have endured 0.00001A current.....I think🤔

I just feel that removing equipotential bond to sink is a bad patch.

kirk.

It was an unusual circumstance the exposed metal of the washer becoming live

He only needed to investigate the issue there ,not interfere with bonding

kirk.

It could be that the sink is extraneous ie: earthy

By fixing the washer issue and removing bonding if it were to happen again he could get a shock across the chest again next time

The shock path through legs can happen regardless of the bonding

Bruthal.

https://www.boards.ie/discussion/comment/121424418#Comment_121424418

Floor route will never approach earthed sink to bare hand, unless floors, shoes etc now are good conductors. Anyway that's a different area. That word "assumption" has never been more used than when someone contacts 230v and the overwhelming assumption is a severe shock. It almost always requires second point of contact to earthed item of metal.

On confirming the sink is isolated enough to remove bonding safely, I dont think that comes in anywhere. Bonding a sink CAN introduce more risk than not bonding it. "Can", being the operative word. It doesn't say "does".

Sink earth shouldn't have been removed. We all agree there. The overlap of what it's function is compared to earth's on appliances has been blurred and/or lost.

Andrea B.

https://www.boards.ie/discussion/comment/121424585#Comment_121424585

But you see, by the posts, it is not agreed that sink earth removal was a bad mitigation in this scenario.

Further, the equipotential scenario not blurred with me.

Fundamentally, in a correctly wired scenario, the sink and machine would have been equal potential, so should not have offered a shock-level fault current path through the human.

Would that be a fair assumption?

kirk.

https://www.boards.ie/discussion/comment/121424619#Comment_121424619

A non-extraneous sink doesn't introduce a potential ie: "usually earth" and in a fault circumstance there is no hazard

They don't necessarily need to be same potential in a fault circumstance

The poster won't have confirmed that either way so he may not be safer now

zg3409

Guy who got a shock from washing machine there may be a fault in the socket supplying the washing machine that was not fixed by replacing or fixing the washing machine. That fault may be still there today increasing the risk of getting a sock from new washing machine. Worst case the new machine has no earth and case could go live due to fault or old lose socket and a family member could get a serious shock some time in the future. Some shocks can kill. Trips are not guaranteed to trip as you already found out.

Bruthal.

https://www.boards.ie/discussion/comment/121424619#Comment_121424619

The only person that seen it as a mitigation seems to be the one who removed the bonding. Maybe i missed others saying it was a good idea. The fact others have pointed out that metal being bonded can sometimes add risk, doesn't mean they think removing the bonding was a good idea.

If a washing machine body becomes live near the bonded sink, that is higher risk than being beside an electrically isolated "floating" sink. Regardless if whether anyone thinks all sinks should be bonded or not, a bonded sink near another metal item at 230v is unlikely to be safer than a non bonded one.

A faulty washing machine can present such a fault in a correctly wired installation. Saying its safe in a correctly wired setup is not really an argument in favour of bonding all sinks. Or is it?

kirk.

I just seen poster said plastic piping so presumably a non-extraneous sink

I've never checked but presumably the reading to MET would be high