Why are taps and bathroom pipework earthed?

It may seem a silly question but it`s always made me think.
Surely if you earth taps and pipe work and a live wire from the main hits earth then current will travel along the pipes and therefore electricute anyone washing at the time!
Also has anyone seen those metal urinals? - they`re earthed too! That made me think!
It`s a serious question. Does it make the bathroom any safer? To me the risks outweigh the benefits, but then what do I know?
Thanx. Tc
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Its all to do with make sure everything is at the same potential (voltage)
Take for example if the house was earthed through the cold water system and there was a short onto the hot water pipe. This would potential put the hot pipe at a different potential to the cold. You then touch the pipe and the little electrons say - hmm easier to go through you than the pipes - ZAP
That's why all pipes in a house should be bonded - and this is typically done as close to the point they might be touched as possible (e.g. the tap)
-- Many Thanks
Francis Clauson Cobham, Surrey, UK

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It doesn't work like that. You need a potential difference between two parts of your body to be electrocuted. Equipotential bonding is designed to prevent this happening.
There are two forms of bonding within the house. Main equipotential bonding ensures that metal services are connected to earth. This prevents a short onto pipework causing all the taps and exposed pipes in the house getting a high potential. As soon as the short happens, the MCB or RCD will trip, cutting the power.
The second form of bonding is supplementary equipotential bonding. This bonds together services within a bathroom to ensure that anything conductive is as the same potential, preventing you getting electrocuted if one part of the bathroom became live and not another.

So is the ground. You don't get electrocuted when going behind a bush.

There are risks, but they aren't great. It is safest to remove the need for supplementary bonding. This can be done by not using electrical appliances and ensuring plastic pipework is used. Then, you don't need the bonding, even for metal baths and radiators. However, when metal services are installed, the supplementary bonding has the dual effect of ensuring the MCB/RCD trips and to reducing any likely potential difference experienced in the meantime.
Christian.
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In an earlier contribution to this discussion,

LOL!
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No, but you would if the bush was at 240V.
Dave
--
And you were born knowing all about ms windows....??


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How would the urinal be at 240V if it is also bonded to earth? Don't you think that, perhaps, the thousands of amps this would imply might perhaps, blow an MCB or RCD?
Christian.
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