Slight shock off water pipes.

[J_N30]

Hello all.

My brother In Law has just purchased his first flat. While fixing a leaking overflow on the bath he got a slight belt off the water pipes. All he has to hand is a volt stick which is indicating voltage, how much obviously we don't know. I've advised him to call an electrician but living in London this may take a while!

In the mean time I'm after any advise on what it could be? Residue voltage from cabling too near pipe work?

I'm presuming his water pipes aren't earth bonded (no gas) would this solve the issue?

Many thanks in advance!

 

[EFLImpudence]

In the mean time I'm after any advise on what it could be? Residue voltage from cabling too near pipe work?

Not if it is correctly bonded.

I'm presuming his water pipes aren't earth bonded (no gas) would this solve the issue?

The water pipe must, if an extraneous-conductive-part, be main bonded at the point of entry to the premises (where practicable, i.e. nearby).
Plus supplementary bonding may be required in the bathroom.

 

[bernardgreen]

For a person to receive an electric shock there has to be two points of contact with the body and the items being touched have to be at different voltages. Birds can perch on 11,000 volt bare over head wires with out getting a shock.

What was the other point of contact when there was a shock from the water pipe ?

Damp plaster on a wall can be contact with a live wire if a cable in the wall is damaged or a switch or socket has a live back box. One hand on that wall and the other touching a pipe that is earthed will create a shock that appears to come from the pipe.

 

[J_N30]

Thanks for the replies guys.

I'm not sure on the ins and outs just that he got a little belt off the pipe while repairing the bath. The baths an old cast iron one and set on a rubber mat.

He's calling an electrician tomorrow but I just wanted to try and give him a heads up before hand.

Presuming the water pipes aren't bonded this i understand this something that needs to be done anyway now, is that correct? Little more into, he's in a second flat if that makes any difference to bonding (not that I'd imagine it would.)

Thanks again all.

 

[EFLImpudence]

Presuming the water pipes aren't bonded this i understand this something that this is something that needs to be down anyway now, is that correct?

Yes, always has been.

Little more into, he's in a second flat if that makes any difference to bonding (not that I'd imagine it would.)

If you mean second floor flat then it should be done in each flat- as you may not be able to ensure it is done anywhere else.



Please let us know the cause if it is found as there are threads like this from time to time but we never seem to be told the outcome.

 

[J_N30]

Shall do. Once the electricians been I'll report back

 

[drgl]

For a person to receive an electric shock there has to be two points of contact with the body and the items being touched have to be at different voltages. Birds can perch on 11,000 volt bare over head wires with out getting a shock.

OT, often wondered about this. Why can a bird sit on a HV wire yet a human when working "hot" via helicopter must wear a protective suite? PD?

 

[bernardgreen]

OT, often wondered about this. Why can a bird sit on a HV wire yet a human when working "hot" via helicopter must wear a protective suite? PD?

There are several reasons but the main one is the potential gradient in the electro-static between the conductors.

For a small bird on an 11Kv circuit the gradient is mostly horizontal so the potential around the bird's head is the same as the wire.

At 132Kv and wires above each other the gradient above the wire is steep enough to create large potential differences above the wire the man ( or woman ) is sitting on. This would affect a person without a conductive suit causing muscles to contract making work impossible.

Also the helicoptor has many sharp points which create an electric wind form those points. This results in a current flowing from wire to helicoptor. Hence the person transfering from helicoptor to wire would be carrying this current if they were not inside the Faraday cage of the conductive suit. If the helicoptor was a smooth sphere it would not create a problem ( other than it could not fly )

 

[jeds]

https://www.youtube.com/watch?v=SkFH8lLvKZ0

 

[JohnW2]

OT, often wondered about this. Why can a bird sit on a HV wire yet a human when working "hot" via helicopter must wear a protective suite? PD?

Bernard has offered some sound theoretical arguments as to possible reasons, but I don't know how important they usually are in practice. It could be that the conductive suit is essentially 'precautionary' and that, in most cases, a person would not actually come to any harm without it.

Kind Regards, John

 

[ban-all-sheds]

If you were given the opportunity to be the subject in an experiment to test that, would you take it? (Ignoring any fear of heights or clambering out of helicopters, agility problems etc)

 

[drgl]

If you were given the opportunity to be the subject in an experiment to test that, would you take it? (Ignoring any fear of heights or clambering out of helicopters, agility problems etc)

No chance! & I wonder who first tested one of those suits?

 

[bernardgreen]

The video shows there is a very large potential difference between the conductor and the in flight helicoptor as shown by a long and high current arc between them. If that arc moved to the man and went through the man's body he would not survive. The suit is essential when the helicopter is close to the wire and the bond wire etween wire and helicoptor is not in place

 

[JohnW2]

If you were given the opportunity to be the subject in an experiment to test that, would you take it? (Ignoring any fear of heights or clambering out of helicopters, agility problems etc)

Of course not - I did only say "It could be that...."! Bernard is quite probably right, given the size of the arc between the helicopter-connected wand and the live wire.

Kind Regards, John