electric shock from shower valve knobs

[charvel]

Hi there
I've checked loads of threads re earth bonding etc, and dont think this is my problem.

I have metal pipes entering the bathroom behind the bath so there is no way of touching them, and have then used plastic from there on. I've fitted a Triton T550I pump, with a fused switch which is located in an adjacent room, the pump connects to a triton mixer valve. the bath is also plastic.

When the valve knob is turned on, the pump fires up fine and works perfectly, only I get small electric shock when touching the chrome covered valve knobs and surrounds.

As I've used plastic pipe for feed and outlet, surely this is not a bonding/earthing issue? any help would be aprecaited, I have the inlaws coming to visit and dont want to cremate them.

 

[sm1thson]

does the instruction manual state the pump requires an RCD? is one fitted? (i would fit one anyway because i dont like mixing water and electricity).

i would say something is leaking electricity to earth and its probably the pump.

 

[charvel]

thanks for your quiock response!

I believe there a an RCD but will check tonight for sure. Even if the pump was leaking to earth, how would it get to the mixer valve if all the piping is plastic?

 

[Teahead]

I think the water held within the plastic pipes might be quite an effective conductor of electricity

 

[TicklyT]

Pure water is actually quite a good insulator. Trouble is water from the main contains additives that increase the conductivity.

Could it be a build up of static electricity at the shower valve, with the water flow through the plastic pipes behaving like the belt in a Van de Graaff generator?

 

[JohnD]

I have metal pipes entering the bathroom behind the bath

So you have metal pipes entering your bathroom. Do you mean that you have failed to supplementary-bond them?

They should be bonded all the the pipes entering your bathroom (e.g. central heating radiator pipes; pipes to hot water cylinder, pipes passing through to loft; lead waste pipe; iron soil pipe) and to the earth wire of every electrical circuit (shower, lighting, shaver socket, immersion heater, central heating pump, electric heater) that enters the bathroom.

If this is done, it is extremely difficult to get a shock in the bathroom because there should be no two metal objects with a voltage difference between them.

so you are wrong when you say

I've checked loads of threads re earth bonding etc, and dont think this is my problem.

However, if it has been done, and you are still getting shocks, please post back and we will explore the possibilities of cable damage in the floor or walls.

As you know, an electric shock in a bathroom can be very dangerous, since the skin is wet (so a better conductor) and you may have naked skin without the benefit of insulating clothes and shoes. therefore, please discontinue use of the shower until you have identified and fixed the problem. If it is an electric shower, start by turning off its circuit.

 

[charvel]

yep I would agree, only I read somewhere today that 1meter of plastic piping with water running through it is still a very poor conductor.

But as the water is the only conductor in the equation, I suppose it must be casuing the problem.

i'll check that the wire is connected the the earth terminal on the pump. Should I attach an earth lead from this terminal to the exposed metal piping before it switches to plastic?

Edit Think JohnD has just answered that for me, I pretty sure that the piping is x bonded in the adjacent room before it enters the bathroom, so am I correct in saying that I just need to bond my pumps earth terminal to the piping as well?

 

[JohnD]

All the pipes, to all the circuits, all bonded together.

The shower pump should be on a 3A or 5A fuse. If bonding it causes the fuse to blow, then it is doing its job and cutting the power.

 

[charvel]

great thanks.

Will check all bonding/earthing tonight and will report back.

 

[JohnD]

p.s. turn off the power before touching the pump and the pipes and the cable.