I'm making some changes in the bathroom - one is switching over copper
to plastic pipe.
What do I do about the trailing earth bonding arrangements that are
left? Just tuck them under the floorboards? Or do the exposed metal bits
(taps and radiator) need to be wired up to these earths?
OK, thanks - yes, they are RCDd.
Seems a pretty thorough principle - the radiator and taps are
effectively metal lumps screwed to something, with no possible path to
anything electrical. Or is it to do with the conductivity of water?
You say no possible path, but what if one of the bracket screws has
almost penetrated a concealed cable?
However, if it does break through and go "live" then as long as the
circuit is on an RCD you should be safe. One of the reasons I have
*slight* reservations about the current principle of having unprotected
circuits to prevent spurious trips taking out the freezer when you are
You could, although abandoned wires are better disconnected at the other
end if that's easy. When forced to abandon a cable / wire its generally
best to leave the exposed ends terminated in some way so that they can't
come into contact with anything (i.e. into a chock box or similar)
There is no requirement (and no point) in bonding bits of isolated
The question you need ask yourself each time, is "can this bit of metal
introduce a voltage into this room?" (even where that voltage is 0V or
earth potential). If the answer is no (e.g. because its not connected to
anything conductive that leaves the room), then its a waste of time
bonding it. Likewise there is no point in bonding things that already
have their path of conduction bonded - so a metal bath where the
incoming pipes connected to it are already bonded etc.
I have had plastic pipes in my CH for over 30 years now.
No plastic pipes or fittings have failed.
However copper tube at my parents house did develop pin holes over a
similar time frame.
Also no plastic valves have failed but some of the brass ones have.
You can't rely on bath taps making a good electrical connection to a
bath. Enamel doesn't conduct and the plastic washers you use don't
conduct. Unless someone has welded a stud on its going to be very hard
to make a reliable connection that will last years.
You only need to bond ?a conductive part liable to introduce a
potential, generally Earth potential". So ISTM:
a. if the bath makes a conductive connection with pipes etc then bonding
the pipes etc bonds the bath.
b. if the bath does not make a conductive connection with pipes etc then
it can't introduce a potential so there's no need to bond it.
I don't see a middle way.
And if both the hot and cold pipes are bonded then it matters even less
as they are the only thing that could introduce a potential (excluding
throwing a hair drier or similar into the bath) and a metal waste pipe.
I'm actually grateful for the more lax regulation of the 17th. It allows
a bit more site related judgement than is possible with prescriptive rules.
My pipes, being chromed and mostly on show would be tricky to bond by
the book. Under the bath - OK. However, I'd have to get a wire over to
the shaver socket and then onto the bog cistern the other side of the
room to do it by the 16th.
In reality, my floor is mostly insulated (tiles on marmox foam panels).
The shaver socket is 1m from the bath and the 2 screws are well recessed
and hard to touch.
The bog cistern pipe is hard to reach even standing next to it, let
alone from the bath (impossible).
The bath is plastic and has a plastic waste.
So all in, if the hot and cold pipes are strapped *somewhere* vaguely
nearby (they are, under the stairs) it's almost impossible to set up a
situation that would be a material risk.
My shower room that we are about to screed is different - got concrete
floor, metal pipes to the shower and you could handle the shaver socket
dripping wet (it's a wet room). So I will probably shove SB in there as
there's definate merit in doing so. It might not be 100% by the 16th -
the clamps will be in the adjacent hall cupboard rather than in the room
itself - but the 17th gives me some design freedom. The end effect will
be as good as 16th SB in any practical way it could be judged.
I'm a little wary of trying to over prescribe solutions. On one hand,
legislating for the worst case/dumbest installer avoids things going
wrong with people who don't like to think things through.
OTOH it tends to become a war of rules, rather than the installer
understanding what he is actually trying to achieve and applying a
perfectly reasonable solution. cf the bonding of every bit of metal in
sight when the whole idea was first introduced. Why? Because installers
did not actually understand what they were trying to achieve. They saw
the "bond metalwork" and blindly applied it to everything.
In theory one can design outside of the regs and mark it as a departure,
but it takes a brave man in this rules based world to put his name to it.
Quite - it's difficult to prove which is most durable. I'm a little
nervous using it on mains pressure, but hey. I would use copper, but I'm
not confident in my soldering skills, and don't like compression joints
that much. And plastic is so quick.
Having worked with plastic now a fair bit, I think it's success largely
depends on the extent to which pipes are properly supported.
In message , RJH writes
Interesting. I am about to be faced with these decisions. The underfloor
heating is all plastic to the manifolds with no hidden couplings.
The boiler piping in 22mm will be copper run in insulated sleeving. That
leaves service plumbing to bath/toilet/sinks etc. undecided.
I intend to route the plumbing through ducts wherever possible so holes
and flexible pipes through joists not hugely helpful.
The creaks from pipe expansion in our current home are noticeable but
not really a nuisance.....
In article ,
Soldering is very easy. Just clean things properly, use a decent flux, and
a adequate heat source. And avoid lead free solder. Practise on some scrap
Bending the copper pipes neatly is the real skill. But great fun.
*Don't* use lead containing solder on potable water pipes, including hot
water! It is regarded as dangerous, and not just a technical
The fact that the water boards have never been forced to replace lead
supply pipes is not a defence or mitigation.