How to test for earth?

[Wombat2]

I was looking at the water heater as it needs a new pressure relief valve and was getting its model number when I noticed the electrician had run an earth wire out of the heater and clamped it to the cold water inlet pipe coming out of the wall - all good you may say but 18" away the cold water supply enters the wall via a copper pipe that is connected to a shut off valve that in turn is connected a black poly pipe coming up through the floor from the pump under the house as we are on tank water.

Would I be correct in assuming if there was a short in the hot water tank the plumbing will become alive as the poly pipe is insulating it from the ground?

How can I check if the pipe work is earthed somewhere and/or would an earth wire from the wire clamp through the floor to an earth stake be sufficient?

[Bros]

I was looking at the water heater as it needs a new pressure relief valve and was getting its model number when I noticed the electrician had run an earth wire out of the heater and clamped it to the cold water inlet pipe coming out of the wall - all good you may say but 18" away the cold water supply enters the wall via a copper pipe that is connected to a shut off valve that in turn is connected a black poly pipe coming up through the floor from the pump under the house as we are on tank water.


What! The HW system should be earthed via the supply cable back to the switchboard to the HW system. Check that this is the case and if it is it is just a belt and braces approach if not be very afraid.

[whippee2]

sounds like it is an equipotential bonding conductor. this brings the section of copper pipe to earth potential. therefore if there was a short in the hws the breaker would trip and the pipe wouldnt become live as it is at earth potential. he has probably connected the equipotential bonding conductor to the earth terminal of the hws j box.
that is it in a nutshell.
hope it make sense

[Wombat2]

Looked a bit closer - the hotwater service is connected to earth via the supply cable from the meter box - the earth wire to the clamp on the pipe is actually running along the back of the flexible condut to the HWS (tied with cable ties) and comes out of the wall with the supply line to the HWS - where it goes/or from - who knows.

The meter box does have an earth wire to the stake.

What ever the wire to the pipe is it is not doing its job cause the pipe work is insulated by the poly pipe.

[applied]

Most likely a equipotential bonding conductor that has been retro fitted to protect the tank side of the copper pipe.

depending on your setup you will most likely find another one at closer to your switchboard protecting the rest of your installation especially if you have copper pipe throughout.


if you relay desperately want too you can check the hws for a solid earth you can by using a multimeter and a long piece of wire.
first check the resitance of the wire then twist it around your earth stake and run it out to your unit now check between an exposed metal part like a screw head and the wire. you should notice almost no difference between the values.

goodluck :)

[Bedford]

Looked a bit closer - the hotwater service is connected to earth via the supply cable from the meter box - the earth wire to the clamp on the pipe is actually running along the back of the flexible condut to the HWS (tied with cable ties) and comes out of the wall with the supply line to the HWS - where it goes/or from - who knows.

The meter box does have an earth wire to the stake.

What ever the wire to the pipe is it is not doing its job cause the pipe work is insulated by the poly pipe.
I've seen this sort of thing before where a sparkie has put in a 3pin base for an exhaust fan, off a lighting circuit (that had no earth), and ran an earth off a copper pipe. I asked why it needed an earth when there was only a 2 pin plug on the fan? and the answer was in case someone plugged something else into it that should be earthed.

Maybe it's something like that.

[Bros]

Looked a bit closer - the hotwater service is connected to earth via the supply cable from the meter box - the earth wire to the clamp on the pipe is actually running along the back of the flexible condut to the HWS (tied with cable ties) and comes out of the wall with the supply line to the HWS - where it goes/or from - who knows.


That's fine it is the bonding to the water pipe that has to be done to the main earth. If you could follow the extra earth you would find it goes back to the main earth. Probably the only place they could find metal pipe.The old method many years ago was to bond to the water pipe below the first fitting coming into the house but now it is anywhere on the water pipe.

Don't worry about it as it is all OK.

[Wombat2]

Thanks guys - that makes sense. When I'm looking for something to do I'll check it out. :roll:

[bigblue]

What whippy said !!


If its a relatively new build or at least been rewired, your installation should have a 6mm2 gr/yl earth wire going to an earth stake and another ( separate ) gr/yl earth wire, sometimes 4mm2 , going to your incoming water supply.

Where the "house" has been plumbed by poly pipe , this bonding earth is not required but if your home is plumbed in copper pipe, but your supply in is in poly, I'd try to attach that bonding earth wire to a " cold water " pipe elsewhere if possible.

Been a while since I took a good look at the regulation book but if the water "supply in" is indeed poly, you may not need the bonding earth at all.:?


Hope I helped rather than hindered !!

[Wombat2]

The house is plumbed in copper but since we are not on mains water but rather tank water we have poly pipe supply from the pressure pump into the house.
The house is 16 years old.

[Glot]

You only need an equipotential bond on any metalic water pipe system that enters the ground. If the house is plumbed in copper but enters the ground in plastic then no bonding is required. Who ever connected the hotwater heater most likely didnt really know what they were doing or were just covering things incase the poly was replaced with copper that ran into the ground. It wont cause any problems leaving it like that.