Why does a bathroom rad have to be earthed to its feed?

[Electrics]

I'm currently in my MIL's house and saw she has an earth connection bolted to the underneath fin of the radiator in the bathroom which goes to the copper feed pipe. Why does this need to be done?

I'm probably being stupid but i can't figure out what it's actually doing since the rad is metal and it's already connected to the pipe by virtue of it being plumbed in, and the pipe goes to the rest of the system which is bonded in 10mm to the mains already.

Why does this need to be done if the system is already earthed elsewhere?

 

[Baddegg]

Probably just a victim of over zealous sparks working to old editions....if it’s metal bond it!.....

 

[littlespark]

It’s from the old regs when everything metal in a bathroom had to be linked together.
”equipotential bonding” basically, make everything equal regarding possible stray voltages.

same at kitchen sinks. Pipe to pipe to metal sink.

 

[Baddegg]

????that’s what I meant ?

 

[pc1966]

The reason for the extra bondage is down to the issue that plumbers are not required to make an electrically sound joint, only one that will not leak water. And in a plumbing system you may well have a mixture of plastic and metal pipework over time.

So in the days before "RCD every circuit" was the mantra, it was "equipotential bond everything". As a result you will generally find bathrooms, etc, that were wired during the 15th/16th edition of the wiring regulations have lots of bonding to ensure no dangerous voltages might be experienced by folk just out of the bath, brushing teeth, etc.

 

[Electrics]

Thanks for the responses guys, lives and learns!

 

[Midwest]

There was some confusion in that era, as to what was extraneous or not, some even bonded metal windows, it got that silly. Fortunately, the next Addition clarified things, as has been said.

 

[Electrics]

There was some confusion in that era, as to what was extraneous or not, some even bonded metal windows, it got that silly. Fortunately, the next Addition clarified things, as has been said.

Wow now that's something i've never seen done. Mental!

 

[Mark Wright]

but equipotential bonding the radiator wasn't/isn't wrong other stuff was.

 

[GBDamo]

but equipotential bonding the radiator wasn't/isn't wrong other stuff was.

The OP states the rad was bonded to its own pipework.

If so, what does this offer?

Unless the rad is fixed to something that is extraneous then I can't see any benefit.

 

[Mark Wright]

erm ok I didn't read that, presumably one of them was liked to some exposed con part at some point.

 

[littlespark]

I remember doing all this as an apprentice...

4mm earth wire to hot and cold pipes under bath, then to the stands of the bath, (even though bath itself was fibreglass), then to hot and cold pipes at basin, then to cold feed pipe to toilet cistern, shower feed if there was one, then onto the radiator.
U shaped clamp with a grub screw to fix it to the rad lip at the bottom, and an M4 machine screw on the back to take a yellow crimp.

Then there was linking every pipe around the hot water tank, same around boiler.

 

[Mark Wright]

The old OSG did show that didn't it, yet some people say just connect one pipe its all linked.

also there's the 50v touch voltage if you've bonded it all in 4mm then linked it to some piddly 1.0mm cpc in the light it's not going to be 50v is it.

 

[radiohead]

Back in the days of 'if it doesn't move bond it' (1980's?) I was at a wedding party in a village hall, in the bogs all the surface pipework had 2 clamps and a little loop of 4mm bridging every single compression joint....and there were a lot of joints, must have taken someone ages!
I also recall going into TLC to pick up some 4mm earth just after the 15th came out only for the bell end behind the counter to refuse to sell it to me because 'it has to be 10mm now'......those were the days. If I had a quid for every poxy sink I grovelled around under struggling to get a connection on that silly little tab I'd be retired now

 

[UNG]

It’s from the old regs when everything metal in a bathroom had to be linked together.
”equipotential bonding” basically, make everything equal regarding possible stray voltages.

same at kitchen sinks. Pipe to pipe to metal sink.

Supplementary Bonding was the term I remember for the extraneous metalwork bonding the minimum bonding conductor size was 4mm² unless it was mechanically protected then it could be 1.5mm² if I'm remembering my 15th edition correctly

 

[ipf]

This is an example taken from a Guide to the 15th edition.
Many a surface single 4mm g/y tucking into a socket and pinned to the grouting......
Watch it brewing up....

 

[davesparks]

The old OSG did show that didn't it, yet some people say just connect one pipe its all linked.

also there's the 50v touch voltage if you've bonded it all in 4mm then linked it to some piddly 1.0mm cpc in the light it's not going to be 50v is it.

No it probably won't be 50V, but that's the whole point, to keep the touch voltage below 50V!

 

[Baddegg]

No it probably won't be 50V, but that's the whole point, to keep the touch voltage below 50V!

I don’t know how you’re not a diplomat Dave! ???

 

[Midwest]

I don’t know how you’re not a diplomat Dave! ???

Or just don't bond everything in sight. Bit like landlords testing their own lets

 

[ipf]

I remember group testing properties for the local authority in the 80's. Doing the bathroom and kitchen remedials were a pain. Earth clips and 4.0mm green/yellow galore. Might just have one or two of those 'radiator earth clamps' stuck away somewhere. It was a weird time, bonding wise, and sometimes makes me wonder about some of todays regs, a bit further down the road.