Wiki: Bathroom Electrics

PeterC wrote:

How does the gas get into the place? (assuming its a gas boiler - same question but for oil if its one of those). It sounds like you may be missing a main bond to that.
It sounds like the CH pipes are the only ones that can do much mischief then, since they probably romp all over the house carrying a potential potential with them ;-)
(imagine a fault in the boiler leaving the pipes live etc)
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John.

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On Sat, 25 Jul 2009 01:04:27 +0100, John Rumm wrote:
<snip> as me mouse wheel is overheating>>>>> The simple way to analyse these things from first principles, is to ask

Gas is via plastic pipe to the meter on the front wall then copper to the boiler. It has no connection to it in the box. This means that the house has no earth other than the CU. Here it looks as if there's an E bonded to the SWA and connected to the CU and to the incoming N.
If the pipes were to become live, at least the rad. in the bathroom wouldn't be to dangerous as there's no other reachable earthed place to touch - it'd need the pull switches to have their covers off or, at a stretch, the fan heater (I could reach that but most people couldn't).
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Peter.
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NT wrote:

Here's one recent case where the benefit of some supplementary bonding would have been far from zero:
http://news.bbc.co.uk/1/hi/england/cornwall/8140632.stm http://www.telegraph.co.uk/news/uknews/5779475/Young-mother-electrocuted-by-bath-taps.html http://www.dailymail.co.uk/news/article-1198470/Young-mother-electrocuted-live-tap-ran-bath-familys-new-home.html
--
Andy

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Andy Wade wrote:

http://www.telegraph.co.uk/news/uknews/5779475/Young-mother-electrocuted-by-bath-taps.html

http://www.dailymail.co.uk/news/article-1198470/Young-mother-electrocuted-live-tap-ran-bath-familys-new-home.html
They don't help matters when the experts start spouting confusing and incorrect terminology:
Jonathan Keane, an electrical expert, told the inquest in Truro, Cornwall, that the home hadn't been rewired or inspected electrically since 1981.
He said: "The combination of the lack of *earth bonding* and the faulty heater created a lethal charge to the taps - killing Thirza when she touched them."
[my emphasis]
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Cheers,

John.

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NT wrote:

I think there are two things at issue here:
One is semantics - yes you could argue that if you are changing nothing, then installing bonding is not "required". However, if no change is being made or contemplated, why refer an article on bathroom electrics in the first place? Chances are if you are looking for information on this, then you plan to make some alterations, at which point this work becomes required. Also if we are addressing competent DIYers seeking to improve bad things on their electrical system, then encouraging them to add bonding when its required but missing, is a "good thing" IMHO. Its cheap, easy to do, and depending on the circumstances can make a life or death difference should you be unlucky enough to have something go bang unexpectedly.
Secondly, there is the issue of severity. I expect based on comments you have made in the past that you don't consider the lack of "required" bonding to be of particular concern. However as I see it (and as Adam highlights, as any form of proper inspection would see it), it is classed as a fairly severe fault.
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John.

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John Rumm wrote NT wrote

these things.
One could certainly argue that. But I think the average householder is well aware that on their list of priorities its extremely low, and in safety terms theyre quite correct on that point.

The near zero number of resulting deaths. When you compare the spend per benefit of equi bonding to many other measures one can take, it simply ceases to be a path worth pursuing unless one is for some reason obliged to do so.

feed.
Unless I'm mistaken, the level of fatalities don't agree with that claim.

But that is an incorrect way to assess safety. There is no end of things that could happen, what matters is which ones do and how often.

Thats a true fact, not semantics :)

Many times people get a PIR done that says you need to fit equi bonding, and they mistakenly believe it to be so. Our article should tell them the truth, that there is no requirement to fit it unless youre carrying out electrical work.
Theres nothing wrong with also adding a section of whether we think you should, but I dont think we ought to tell porkies by saying yes you're required to do it.

So opinion is mixed. If, as we did once before, guess the average cost of installing it, multiply by the number of houses, and divide by the number of lives it saves per year it works out at a phenonmenally high price per life, when many other simple domestic works for the same money/time would yield far greater safety improvement. It just isnt warranted on safety grounds.
Why not...
Lets say install cost 20 materials, 4 hours labour for a diying novice, including going and getting the bits. Total cost 20 + 4x7-15, perhaps 40 as a balpark figure = 60 total
x20 million houses = 1.2 billion
If this saves one life every 5 years, thats a cost of 6 billion per life saved, which is orders of magnitude higher than a whole swathe of more practical constructive measures one can take.

That only shows a recognised flaw in such testing, namely that the results given are sometimes entirely unrealistic and to encourage needless spending.
NT
note top and bottom replies
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wrote:

Thats a true fact, not semantics :)

Many times people get a PIR done that says you need to fit equi bonding, and they mistakenly believe it to be so. Our article should tell them the truth, that there is no requirement to fit it unless youre carrying out electrical work.
Theres nothing wrong with also adding a section of whether we think you should, but I dont think we ought to tell porkies by saying yes you're required to do it.

So opinion is mixed. If, as we did once before, guess the average cost of installing it, multiply by the number of houses, and divide by the number of lives it saves per year it works out at a phenonmenally high price per life, when many other simple domestic works for the same money/time would yield far greater safety improvement. It just isnt warranted on safety grounds.
Why not...
Lets say install cost 20 materials, 4 hours labour for a diying novice, including going and getting the bits. Total cost 20 + 4x7-15, perhaps 40 as a balpark figure = 60 total
x20 million houses = 1.2 billion
If this saves one life every 5 years, thats a cost of 6 billion per life saved, which is orders of magnitude higher than a whole swathe of more practical constructive measures one can take.

That only shows a recognised flaw in such testing, namely that the results given are sometimes entirely unrealistic and to encourage needless spending.
NT
Hi
I do not accept that there is a flaw in a test procedure that correctly identifies a fault an electrical installation.
The Wiki article on bathroom electrics does have a link to supplementary bonding requirements and that is good.
Maybe the words
"Unless an installation complies with the latest requirements of the 17th edition then supplementary equipotential bonding is required."
could read
"Unless an installation complies with the latest requirements of the 17th edition then supplementary equipotential bonding should be installed to BS7671 regulations if you ever want a pass certificate on your house electrics when you want to sell your house and do not want the buyer to start knocking money off if the buyer is looking for faults"
or
"Unless an installation complies with the latest requirements of the 17th edition then supplementary equipotential bonding should be installed to BS7671 regulations"
For some reason there seems to be far much trouble caused by using the word "required".
Adam
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NT wrote:

Not really - the wiring regs still say its required. The fact that there is no legal compulsion to update the exiting install to follow those requirements does not make the requirement go away.
We could include extra verbage at the top that highlights what is meant by "required" etc, but then why single out this article? Few of the others contain similar. Its not as if this one is focussed on specific advice on a task like changing a CU or installing outside power feeds. Its just an overview of the right things to do in bathrooms and a heads up as to why they are different from other rooms.

PIRs don't include an in depth analysis of the implications of things like missing bonding. In some cases you could argue that a particular installation has very few if any failure modes where EQ bonding would mitigate. Equally however, there may be some that make it very well worth having.
By all means tell em that they are not legally obliged to carry out the work; but if the PIR has highlighted a fault that should be fixed, unless they are in a position to carry out enough analysis to say if there is a better cost benefit trade off to be had elsewhere, they ought to carry out the fix. Any other advice would be reckless.
A couple of example scenarios:
e.g.
1) 16th edition PMR head end, small shower room, plastic pipes everywhere and the only electrical circuits in use are the lighting one, and a spur from a upstairs ring circuit to feed a towel rail. The lights are SELV downlighters. The actual risk of serious shock in this circumstance is negligible. Since mains never manifests in the room anywhere other than the towel rail, and there are no other extraneous conductive paths (the CPC of the lighting circuit does not present in the room - the metalwork of the down lighters is floating, the switch is non conductive and out of reach on a string). According to to the Regs Bonding is still required, however the implications of ignoring the requirement are to all intents nil as things stand.
2) 15th edition install, re-wireable fuses, TT head end (overhead wire supply), no bonding at all (main or supplementary), a VO ELCB is connected inline with the main earth provided by a gas pipe. There are a number of borrowed neutrals and neutral earth faults. a 13A socket is installed beside the sink to allow a hairdrier etc be plugged in. Bathroom has CH piped towel radiator, metal pipes to all taps and cistern, and an electric shower, plus fan heater, and some class 1 luminaries on a low ish ceiling controlled by a nice polished chrome wall switch next to the shower. In this case there are any number of fault scenarios that could present serious and life threatening shock hazards i.e. faults that could leave high touch voltages on metal surfaces for extended periods, with ready access to an independent earth close to hand. Now obviously a PIR would highlight all manner of shortcomings here. The long term solution would probably be a package of measures including a re-wire or at least a new head end. However installing main and supplementary bonding PDQ would be cheap and effective way to lower the rooms status from "death trap" to something more acceptable.

Depends on your interpretation of required. See comments above.

Statistical exercises like this can be useful for setting government policy[1]. However we are not really concerned with overall impacts, targets, costs to the nation etc, and are focussing on one electrical installation. What is best for the majority has no bearing on what is best for Joe Internet Searcher, 32 Acacia Avenue who has just moved into a place and had a PIR throw up reams of faults that he does not understand; missing bonding being one of them. The only sensible advice we can give in a general purpose guidance article is to say you need to be lead by the professional opinion of the people you have paid for advice and here is what the bonding does and how it works if you want to know. The implications of it not being there may be trivial, or may be very serious, we can't tell you from here.
(Note also this is partly a circular argument. We have very safe electrics in the UK as a general rule - both fixed, and appliances (the former more so than the latter). Deaths are very rare, and injury relatively rare. Part of the reason for this is that we do specify and install safety measures like EQ bonding, RCD protection and a host of other measures. Its almost impossible to say how many extra injuries etc we would have had without these measures, other than a casual observation that numbers of deaths etc have been falling for years (at least until the intro of part p anyway), and electrical installations as a whole have been getting better as more are updated and rewired to current standards).

So the question that matters to me is, could that 60 save the life of someone in the family should something go wrong? The answer is usually yes.
So the next question is, how likely is it that something will go wrong in a dangerous way, with my particular installation, that means I would get to "use" that 60s worth of investment and hence make it worth spending here and not on mitigating some other risk. If the answer is "high to moderate" then you spend the 60. If the answer is "I don't know" the next question is can I get sufficient expert analysis at less cost, that would tell me if its going to make a difference. If the answer is no, then you spend the 60. If the answer is yes then you spend the money on that instead, and then possibly spend the 60 afterwards as well depending on the outcome.

We are not talking about spending billions, since we are not writing an article to advice policy makers. We are talking to the individual ones looking at your 60 bill.

Its a flaw in the process that one accepts since it controls the cost of such testing. A PIR plus the cost of remedial action is in many many cases going to be significantly less that the cost of a test with a detailed analysis and risk assessment to go along with it. Also doing the work once often saves repeating the exercise later to justify that something non standard is actually ok in this circumstance.

Agreed; and sometimes the results will be highly realistic, and encourage spending on something that needs doing as a matter of urgency.
How do you differentiate without detailed technical knowledge?
Perhaps there is a whole new article there; "My PIR said X, how much notice should I take?".
[1] although following the logic, part P would never have been introduced - which shows up the disparity between stated and real agenda.
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Cheers,

John.

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snip
If I get the time I'll address some of the confusion here
NT
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it means that, by definition, it isn't required for most houses.
There is simply no requirement for most houses to be to current standards, and the great majority aren't.

You removed the statement that it was required if doing electrical work, replacing it with the erroneous claim that its required in all cases.

There is simply no basis for saying the missing bonding should be fixed. The cost/benefit analysis shows it to be at best worthless, and the legal position is that it is not required in most cases.

Telling the truth about the legal position is not reckless or unwise.

You're missing the point I made last time. You may /imagine/ some unbonded bathrooms to be deathtraps, but the figures (ie facts) show very clearly that they're not.

it seems evident that cost/benefit is relevant, and is in fact precisely the grounds on which we make decisions as to what to spend on safety.
Lets take an example: imagine you have 2 options, to spend 60 on getting the car's brakes fixed or to spend on equi bonding. You know that there are around 3500 deaths per annum from car crashes, and around 0.2 from bathroom electrocutions. In each case spending the 60 would decrease those risks, but not to zero. Its obvious what one would choose, the question is how? If you don't think its on cost/ benefit ratio, on what basis do you make the choice?

If there are reams of faults, a rewire would be a lot more sensible than fitting equi. And if Joe were too broke to do that, spending the money on fixing some faults would be far more worthwhile than fitting equi. And once all the faults are fixed, then adding equi becomes valueless anyway in safety terms.

I don't see any reason for us to even comment on that. Re equi bonding, why not just state the truth, that its required when doing electrical work?

yes we can, we know ballpark figures on this.

the majority of domestic installs in the UK predate equipotential bonding, and a large percentage still have no RCD. The national death rates from electrocution apply to all systems, risks added up, not specifically to newer one with rcd/equi.

The answer is fairly clear: Yes in approx 1 per 5x 20 milion households = 1 in 100 million odds of it being of any use in each year.


we know the answer is around one time per 20 milion households per year. 1 per 100 million.

That misses the point entirely. The question that addresses is if we have finite financial resources, as we always do, what measures are worth taking using those resources. The calculation shows that equi bonding is a long long way from being worthwhile. As a comparison, the NHS has an across the board spending ceiling of 30,000 per qaly. That is our current national level of spending on safety measures.

Reporting the omission more realistically as just NTCS would cost zero more.

national death statistics. Then one calculates approx cost/benefit for safety measures.

or 'what does this mean in real terms?'

Spending money on safety measures that yield little only leaves less money to spend on safety measures that are of genuine importance.
In this case the cost/benefit ratio is 1/ 6billion to 1/ 30k = a ratio of 200,000:1. IOW spending that 60 per person on useful measures could save 200,000 as many lives as by spending it on equi bonding. So realistically, its fatal in many cases.
Given this, why claim its always required when it isn't?
Or if you think it is required for all houses to meet latest wiring regs, which act of law do you believe says so?
NT
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NT wrote:

We can go round in circles on this. Yes I agree there is no legal requirement to bring an old install up to current standards. Unless you change anything. However that just means that it is allowed to to be non compliant with the technical spec. The spec's requirement's however have not changed.

Your cost benefit analysis is looking at it from the wrong perspective. I agree that there would be no point in legislating that all properties must be inspected and have it added if required and missing. The cost would be disproportionate to the benefit.
However that is a very different argument from the case where you have been informed by a professional that the installation is at fault and you need to asses the significance of that fault.

If you are doing nothing to an installation, then you are not obliged to upgrade it to meet the requirements.

We are not talking about the legal requirements. We are talking about giving good advice, and doing a proper job. We have already stated the legal position. By all means add further words if you think it would help.

Again you are attempting to carry out an epidemiological study (without access to the raw data I might add). We are dealing with rare events and small sample sets. We may hear about the deaths, we probably don't hear about the vast majority of injuries and shocks.
It remains the case that EQ bonding in a bathroom is a cheap and easy fail safe measure that may well be conclusive in the event of another failure.

You don't provide enough information to make the choice. If your particular bathroom happened to be like the one that Andy W posted a link about, then the liklihood that you are going to fall into your 0.2% is very nearly 100%. Its a pretty good certainly that someone would get a serious shock before long.
If money is so tight, then why pay the 200 - 400 for a PIR if you are not going to be in a position to fix any faults it finds? You would be better of fixing the car and spending some time reading about what constitutes a safe electrical system.

I don't agree. EQ bonding is a fail safe technology. Fixing current faults is no protection against those that may occur in the future. Bonding is.

We have said you are not legally obliged to upgrade. That is closer to the truth I would say.
Most informed people asked to say where the *requirements* for electrical installations are specified, would say BS7671. According to that, bonding is required (17th edtn spec installs excepted).

Without detailed knowledge of the installation in question you don't, you only have stats which by definition are not specific.

Do you have a source for this claim? EQ bonding goes back to at least the 14th edition - so that is 1966. I would be very surprised is pre WWII wiring installs were still in the majority.

useless analysis - we are not talking generalisations. I want to know what it means for *my* installation.

we don;t actually - even in general terms. There could be hundreds of people who are alive, well and uninjured or hurt that are possibly even unaware that they were saved by a protective system such as those being discussed.

No, I can't see the logic here.
Depending on the *actual circumstances* the chance that a protective measure will have a decisive effect on the outcome will vary in probability from nil to 100%. Personally, if the risk in my house is nearing 100% I am not going to draw any comfort from the fact that according to national statistics I died in a very improbable way.

yup. However to do any good, it is going to have to impart sufficient technical know how to make a decision based on the facts of the actual installation, and not just state heuristics based on statistical likelihoods.

yup, I agree.

woosh...
How about because the requirements say so?

I believe one is not legally obliged to upgrade to meet the current requirements. If you want the requirements they are available from Amazon et al.
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John.

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ok, to save going round this loop any more, I have added the following words to the earthing and bonding article:
On the subject of main bonding:
"Note that if the main bonding is not present, it is considered to be a serious electrical fault. As a result anyone carrying out modifications to any part of an electrical installation should also check and rectify any faults in this area at the same time. Note that although there is no general legal obligation on house owners to upgrade the electrical system to meet the current requirements as laid down in BS7671 (the "wiring regs"), it is not uncommon for professional electricians to refuse to undertake any other work unless their are also instructed to perform any required remedial work on the main bonding at the same time."
and on the supplementary bonding bit:
"Again a householder is not legally obliged to upgrade or install supplementary bonding when it is required (by the wiring regs) but missing, (or in some other way substandard), unless they are carrying out other work in the same room. "
I have also added a note to the bathroom article to the effect:
"One should also keep in mind that a room containing a bath or shower is classed under Part P of the building regulations as a "special location". This means that other than like for like changes of accessories etc, or the installation / upgrading of supplementary bonding, nearly all electrical work will be classed as a "major work" for the purposes of part P. Hence to comply with the requirements the work would need to be carried out under a building notice, or completed by a person who is a member of one of the various part P competent persons schemes. "
--
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John.

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wrote:

In England and Wales?
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Geo

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Geo wrote:

Yes good point - Probably Northern Ireland as well, but Scotland has its own foibles.
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John Rumm wrote:

I suggest that should say "notifiable work" to avoid any confusion with the major/minor distinction between work done on a 'normal' EIC, as opposed to a minor works certificate (a separate, albeit related, issue).

No Part P in NI, AIUI, unless things have changed.
--
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Andy Wade wrote:

Yes, well spotted - even a minor work would be notifiable in a bathroom.

The irony is that we make "Irish" jokes, and yet this time its on us it seems!
wiki updated...
any more observations before I take the "under construction" header off it?
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John Rumm wrote:

The picture at
http://wiki.diyfaq.org.uk/index.php?title=Image:Equi_bond_outdoor_1537-2.jpg
in the bathroom article shows an incorrectly fitted BS 951 earth clamp. The embossed aluminium label should be fixed through one of the round holes, under the lock nut on the clamping screw.
--
Andy

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I hope not. Something as soft as aluminium under the lock nut would encourage it to undo IME.

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They are usually under the locknut and cause no trouble. Having said that the requirement is merely that they are visible and not [easily] removed. Complaining about *how* they are attached is ridiculous.
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Bob Mannix
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They are so soft they are easy to remove however they are attached. You just pull or even bend them a few times.
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