Supplementary Bonding in Bathroom

[eddieward10]

I have recently re-fitted my bathroom and when doing so used a combination of copper piping and plastic connections for the hot and cold water supplies. Don’t ask why I didn’t use plastic piping as well – probably because the incoming hot and cold water pipes coming into the bathroom from the kitchen were already copper

The only electrical appliances in the bathroom are the halogen downlights and an extractor fan – both of which are low voltage DC type appliances with the transformers located in the attic. Both are operated from the light switch which is located outside the bathroom. The height of the bathroom is 2.4 metres and as such some of the lights would I believe be in a zone 2 location because of their position in relation to the bath.

The original bathroom which was very old had the incoming cold water pipe earthed back to the main consumer unit and that was all. And the new cold and hot water feeds coming into the bathroom are also earthed up to the point where they reach the first plastic connectors

The radiator in the bathroom was replaced but the piping kept as is and all pipes and fitting are metal.

Can someone please advise whether any supplementary bonding is necessary between the downlights, metal water pipes and metal radiator pipes and if so whether I also need to electrically bond across all plastic pipe fittings.

Many thanks
Eddie

 

[Pensdown]

I'm not sure why your question has been siting around but I will try and help

If you put the regs to one side for a moment and have a think, the purpose of bonding in a bathroom is to ensure all exposed metalwork is at the same potential.

You don't need the old connection that goes back to the CU as this may add a problem in the event of an earth fault on your system Your goal is to make sure all metallic parts within your bathroom are at the same potential, and that may mean bonding across plastic fittings as these in can isolate other metallic parts from others that have been bonded to a common potential.

 

[ban-all-sheds]

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http://www.iee.org/Publish/WireRegs...tumn_plastic_pipes_to_bond_or_not_to_bond.pdf
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[eddieward10]

thanks for the reply guys. had already come across this link ban-all-sheds, but was still unclear.

I see your point pensdown and was actually of an opinion that it was perhaps safer not to connect up to the consumer box earth because of what i'd read in the above link.

however i can't see what the benefit is of bonding all exposed metal surfaces is if none of them are ultimately connected to earth. Sure they'll all be at the same potential, but is that any benefit if any current present in event of fault has no where to go.

Also if i do bond all exposed metal surfaces, then heating system is bonded to earth CU elsewhere in house and so all metal parts will then be earthed anyway

perhaps i'm missing the point somewhere

eddie

 

[Spark123]

The whole point of supplementary bonding in a bathroom is to create a faraday cage. The bonding is done locally to minimise the potential difference in the event of a fault. Only metalic parts which can introduce a potential into the bathroom are required to be bonded (extraneous and exposed conductive parts). Items fed by plastic pipes and not in contact with anything else which makes them extraneous (such as metalic building structure) do not require bonding.

 

[eddieward10]

thanks Spark.

From whats been said because the hot and cold feed water pipes which enter the bathroom (hidden away uder the bath) are imeediately connected by plastic connectors to the rest of the plumbing inside the bathroom, I can forget about bonding all subsequent metal piping, taps etc. on the hot and cold water circuits.

The only other metallic thing coming into the bathroom is the radiator - which is fed by metal pipes and fittings. But as its the only thing then theres nothing to spplementary bond it to anyway.

Am i correct in this assumption?

 

[ban-all-sheds]

No you're not - the use of plastic connectors on copper pipes does not provide sufficient isolation. Even though pure water is not a good conductor, a few mm of it will be good enough to make the pipes, taps etc extraneous-conductive-parts.

 

[Spark123]

You will need to bridge across the plastic connectors using suitable clamps and cable left accessable for inspection, solder suitable wire across the joint or replace the joints with metal ones which can provide electrical continuity.

 

[ban-all-sheds]

Why not just apply bonding after the plastic connectors? What does bridging the connectors buy you?

 

[Spark123]

In case the pipework is required to be used as a protective conductor.

 

[eddieward10]

More complicated than I thought this.

Ok so i'm going to bridge every plastic connector in the hot and cold water systems with cable and clamps (which is actually what i'd originally done).

And i'm going to suplementary bond between the radiator pipes and the water pipes to ensure equipotential accross these two systems in the bathroom.

Hows that sound Spark?

 

[Spark123]

Sounds OK to me, is the bathroom still in bits? I ask as it may be advisable to also run a supp. bond to the lighting circuit for future use. (This bond is not required for selv lighting but is if it is ever replaced with mains)

 

[eddieward10]

Thanks for your guidance spark

bathroom still sufficiently in bits to allow me to bond between light circuit and pipes

can i ask one more (probably silly) question - and this doesn't concern the bathroom. The main earth bonding point between the CU and the water pipe which is downstairs needs to be moved because the piping has been re-sited. The existing earth cable no longer reaches the new position. Is there an approved connection method to add an additional length of cabling to the existing earth cable or do the regs specify it should be unbroken

thanks

 

[Qedelec]

Most professionals would prefer to see it unbroken, and if its not too long I would replace it, but if that's not feasible join it with crimps and a rachet crimper or solder join.