Thread: Earth to water pipe? IMportant?

Originally Posted by edddo

I have been cleaning some rat **** from around the electric HW system in the cabin near the house.
I noticed a thick (abt 4mm) wire ( green with a yellow stripe) terminating near a copper water pipe...but not connected to it and a broken clamp next to it.
I assume it is/was some kind of earth..the HW system works fine.
Is it important?
Should I get a leccy in to have look?

The wire and clamp are the same as in pic attached - this one is in the house.

Thanks - just dont have a clue with electricals.

IMG_2550.jpg

Call an electrician and get them check your earthing system
Your house may have had alterations and it may be redundant if not get it reconnected
The earth bond to water pipes is there to protect you from getting electric shocks when using water
It has probably been like that for a while and you haven’t been shocked but if a fault occurs your fried



Gav

Originally Posted by Gav 110

Call an electrician and get them check your earthing system
Your house may have had alterations and it may be redundant if not get it reconnected
The earth bond to water pipes is there to protect you from getting electric shocks when using water
It has probably been like that for a while and you haven’t been shocked but if a fault occurs your fried



Gav

What he said - get it checked, you may not have an earth. All good when things are going well, potentially catastrophic if something goes wrong.

Originally Posted by Homestar

What he said - get it checked, you may not have an earth. All good when things are going well, potentially catastrophic if something goes wrong.

As this poor lass found out: Denishar Woods electric shock report fails to lay blame for accident that caused brain damage - ABC News

Revealed: what caused Perth girl Denishar Woods’ electric shock | PerthNow

Originally Posted by Homestar

What he said - get it checked, you may not have an earth. All good when things are going well, potentially catastrophic if something goes wrong.

100%, but it also can't hurt to reconnect it. Earth, as pointed out, is vital.

Originally Posted by p38arover

As this poor lass found out:

Not quite. That house had a functional earth, it was a broken neutral in a very specific set of circumstances that did the damage. In fact if the earth hadn't been intact that particular failure mode that did the damage wouldn't have occurred. (other bad stuff would have happened though)

Tragic circumstances.

While we were renting the place in Melbourne, Telstra came out to fix a line fault and the tech sliced the main earth while he was there "Yeah mate, we used to use an earth years ago but we don't need them now and it was in the way". I gave the owner a quick call and Mr Telstra was back in a couple of hours to hook it back up. 'Ah yeah mate, didn't notice it ran all the way back to the meter box, thought it was just one of ours".

Muppets.

Originally Posted by BradC

Not quite. That house had a functional earth, it was a broken neutral in a very specific set of circumstances that did the damage. In fact if the earth hadn't been intact that particular failure mode that did the damage wouldn't have occurred. (other bad stuff would have happened though)

Tragic circumstances.

While we were renting the place in Melbourne, Telstra came out to fix a line fault and the tech sliced the main earth while he was there "Yeah mate, we used to use an earth years ago but we don't need them now and it was in the way". I gave the owner a quick call and Mr Telstra was back in a couple of hours to hook it back up. 'Ah yeah mate, didn't notice it ran all the way back to the meter box, thought it was just one of ours".

Muppets.

I think P38 and Tins are right, don't be confused about the "start" of the fault and the "cause" of the injury, seems like the garden tap and assoc. piping was not sufficiently bonded to earth, if at all, and when the poor girl touched it she became a/an even better return path to earth, resulting in a tragedy. Bonding to earth is more properly called "equipotential bonding" and as such should mean that all earthed parts are at the same potential, so therefore a voltage difference cannot exist between them and so no current flows, or more precisely no eddy current flows. The "parallel path" referred to in the Perth Now article should've been so small that only a tingle should've been felt if anything. A few plumbers have been hurt this way by cutting metal pipes to repair or replace, not realising they are actually cutting an earth path, or creating a problem by replacing metal pipes with plastic as in doing so they have changed the earth path. Unfortunately I have heard horror stories like an electrician cutting off an earthing rod/stake, as it was too difficult to hammer into the ground more than a foot or so!

Originally Posted by RANDLOVER

I think P38 and Tins are right, don't be confused about the "start" of the fault and the "cause" of the injury, seems like the garden tap and assoc. piping was not sufficiently bonded to earth, if at all, and when the poor girl touched it she became a/an even better return path to earth, resulting in a tragedy.

With the greatest of respect, I'm pretty sure I'm not confused.

Equipotential bonding is never ideal, because _everything_ has resistance. My opinion didn't come from the "Perthnow" article, it comes from the final report and a voice inside the Department of Energy Safety and it's an incident that has been discussed over the dinner table for years.

Read the report. All bonding was in place, the earth stake was correctly configured and all earthing tested out to spec.

There was an estimated 38A of load on the premises at the time of the incident resulting in a 219V potential between the tap and earth which would indicate an aggregated earth impedance back to the nearest earth/neutral sources of ~5.7 Ohms. That's not at all unusual for the dry sandy soil of Perth. In normal circumstances with a functioning neutral link, the Earth impedance would be measured as an aggregate of all the nearby houses at low currents. Without the neutral link you are reliant on the immediate route to the nearest earth point(s) and with a significant load those are quite non-linear. She was standing on wet earth, so surface area vs surface area of the pipes/earth stake, she was the bigger and more conductive target.

I'm not entirely sure *how* they estimated the load when the neutral impedance was so high, but these guys do it for a living.

So I stand by my original post. If the earth had not been adequately bonded, that tap wouldn't have been anywhere as live as it was. Other bad stuff would have happened, but it's only speculation as to the severity of that. What actually happened was tested and reproduced.

Your comment on her being "an even better path to earth" is absolutely correct, but not because the electrical installation was deficient, rather that ideal equipotential bonding is a myth and the soil the house was built on wasn't designed to carry 38A and her path to the neighbours earth stake(s) was better than the actual stakes/buried pipes.

Edit : Report : https://www.commerce.wa.gov.au/sites...ember_2019.pdf

Originally Posted by BradC

................................

There was an estimated 38A of load on the premises at the time of the incident resulting in a 219V potential between the tap and earth which would indicate an aggregated earth impedance back to the nearest earth/neutral sources of ~5.7 Ohms. That's not at all unusual for the dry sandy soil of Perth. In normal circumstances with a functioning neutral link, the Earth impedance would be measured as an aggregate of all the nearby houses at low currents. Without the neutral link you are reliant on the immediate route to the nearest earth point(s) and with a significant load those are quite non-linear. She was standing on wet earth, so surface area vs surface area of the pipes/earth stake, she was the bigger and more conductive target.

I'm not entirely sure *how* they estimated the load when the neutral impedance was so high, but these guys do it for a living.

So I stand by my original post. If the earth had not been adequately bonded, that tap wouldn't have been anywhere as live as it was. Other bad stuff would have happened, but it's only speculation as to the severity of that. What actually happened was tested and reproduced.

Your comment on her being "an even better path to earth" is absolutely correct, but not because the electrical installation was deficient, rather that ideal equipotential bonding is a myth and the soil the house was built on wasn't designed to carry 38A and her path to the neighbours earth stake(s) was better than the actual stakes/buried pipes.

Edit : Report : https://www.commerce.wa.gov.au/sites...ember_2019.pdf

Thanks for the link to the report I hadn't seen that, lot of fluff in there, but I and Wkipedia ( The NIOSH states "Under dry conditions, the resistance offered by the human body may be as high as 100,000 ohms. Wet or broken skin may drop the body's resistance to 1,000 ohms," adding that "high-voltage electrical energy quickly breaks down human skin, reducing the human body's resistance to 500 ohms".^[17]
The International Electrotechnical Commission gives the following values for the total body impedance of a hand to hand circuit for dry skin, large contact areas, 50 Hz AC currents (the columns contain the distribution of the impedance in the population percentile; for example at 100 V 50% of the population had an impedance of 1875Ω or less):^{[18] Electrical injury - Wikipedia )} agree with most of it's findings of fact.

However I don't agree with the Appendix that the only solution is smart meters, and I think the power supply and generation companies would like, actually love you and more importantly the general public to believe that "equipotential bonding is a myth". If they ran a better and therefore more expensive system like running an earth conductor from the star point of local transformer in the street/suburb to the customer's premises, they wouldn't have to rely on poor ground resistance/conductivity to protect the public. An even better and more costly alternative would be to run an earth all the way back to the generators star point, creating a "safety transformer" sort of effect, feel free to suggest this to the "voice inside" at your next dinner party. The report also glosses over the fact that her injuries were so tragic because she basically lay in water being electrified the whole time until the power was turned off, I had wondered about that, seemed totally disproportionate, once again "start of the fault vs cause of the injury".