Is it dangerous if there is a mains fault on a potable water pipe?

[gen x]

Both the main electrical cable (three-phase, line to neutral=230V, line to line =400V, 50Hz) and the water supply line(ppr pipe) are underground, below the earth in the garden, located next to each other, the main electrical power has damaged insulation, bare live line is exposed to a water leak from a broken main potable water line. So fault contact happen before RCD.

Could this situation be dangerous, especially if a person is showering at the same time? I am trying to understand whether this could create a shock risk to occupants and how effective will be RCD in house(downstream from fault contact) or breakers in upstream transformer(power source) would be in such a scenario.

House has classical wiring system,so every electrical device has ground wire connect to metal housing, water heater in bathroom as well.

 

[DaveE]

The building codes, at least in California, require that metallic water pipes be grounded to earth and that the neutral conductors are grounded at the service entrance. So people in the house should be safe. OTOH, I would still consider this a dangerous situation for other reasons.

 

[Averagesupernova]

So fault contact happen before RCD.

This still could trip an RCD depending on the path of the current on the water pipe. The pipe from the house to the shutoff valve may be metal but often switches to plastic at that point. Therefore the current path goes back into the house on the pipe. Depending on how the RCD is set up it may trip. In the USA residences would not have what we call a GFCI in a place that would cause a trip. It is not uncommon for a metal water pipe to be carrying several amp in the USA.

 

[Lnewqban]

Is there any grounding for the water contained in the plastic pipes system?
Could the grounding of the water heater be considered a water grounding?

 

[DaveE]

Is there any grounding for the water contained in the plastic pipes system?

Plastic pipes don't require grounding (because you can't). Metal pipes do. If, in distribution, they switch between them, the metal must be grounded. Does burying a galvanized steel pipe in the ground count as grounding it? IDK, but pounding a 6' copper rod into the ground doesn't seem that much better than burying a big pipe.

At your house, metallic water pipes should be grounded. Because you don't really know the answers to how things were actually done elsewhere.

This thread is about electrical shock hazard, but grounding water pipes is also important for other reasons, like galvanic corrosion.

In any case the answer for people that actually need to know lies in numerous building codes and technical standards. If y'all really care, you'll hire an expert or start reading the appropriate standards.

 

[gen x]

The building codes, at least in California, require that metallic water pipes be grounded to earth and that the neutral conductors are grounded at the service entrance. So people in the house should be safe. OTOH, I would still consider this a dangerous situation for other reasons.

What mean grounding, connect pipe to ground wire(green or green-yellow wire) that coming from transformer or connect to Planet earth with wire? If pipes are metal and they lay under the ground, arent they grounded by itself to planet earth?

When live line connect metal housing of some electrical device, dose current travel back to transformer through, ground wire, neutral wire or planet Earth(underground)?

 

[DaveE]

If pipes are metal and they lay under the ground, arent they grounded by itself to planet earth?

Yes, I think so. But your water utility will actually know the pertinent rules and the specific construction involved (like coatings and such).

When live line connect metal housing of some electrical device, dose current travel back to transformer through, ground wire, neutral wire or planet Earth(underground)?

This could be kind of complicated, but basically the current will flow trough the PE (protective Earth, or "ground wire") conductors back to the neutral connection at the distribution transformer. Ideally through wires designed to carry that current.

There may be several variations of the details based on where you live and the age of your wiring. If you really care, you'll have to study a bit.

 

[gen x]

Yes, I think so. But your water utility will actually know the pertinent rules and the specific construction involved (like coatings and such).



This could be kind of complicated, but basically the current will flow trough the PE (protective Earth, or "ground wire") conductors back to the neutral connection at the distribution transformer. Ideally through wires designed to carry that current.

There may be several variations of the details based on where you live and the age of your wiring. If you really care, you'll have to study a bit.

Does house need PE wire connect to earth in garden, if yes why?

 

[DaveE]

Does house need PE wire connect to earth in garden, if yes why?

In general yes. But it may depend on local codes. I really only know about California.

The reason is that the utility transformer may not have a ground reference. Anytime you have an isolated source, like a transformer, you must ground the output circuit somewhere, somehow.

 

[gen x]

In general yes. But it may depend on local codes. I really only know about California.

The reason is that the utility transformer may not have a ground reference. Anytime you have an isolated source, like a transformer, you must ground the output circuit somewhere, somehow.

But why we even need ground reference, if we have PE wire that return current back to transofrmer in case of fault?
We have PE wire just to make RCD work?

 

[DaveE]

But why we even need ground reference

Because you are probably standing on the ground when you touch things.

 

[Lnewqban]

Plastic pipes don't require grounding (because you can't). Metal pipes do. If, in distribution, they switch between them, the metal must be grounded.

Copied from the OP:
"... and the water supply line (ppr pipe) are underground, below the earth in the garden".
Unless I am missing it, no existing metal pipe has been mentioned in the description.

 

[DaveE]

Unless I am missing it, no existing metal pipe has been mentioned in the description.

Which doesn't change my statement that metal water pipes must be grounded, accessible or not. Although nonexistence is a valid exception.

Because questions like this are seldom (if ever) adequately described, I find it easier to just cite standard practice and general requirements to avoid a game of 20 800 questions. That's why people pay engineers, to solve specific problems. I'm not being paid, and I'm not sure I care if this water pipe is accessible.

PS: It's an odd pedantic discussion anyway. It strains credibility for a buried metal pipe to not be inherently grounded. But I'm sure there's a fanciful scenario (that may soon be posted here). Something about chiseling a trough in a big granite slab?

 

[sharps4590]

As per NEC if electric lines and water lines are in the same ditch there is to be 2 ft. of separation. I'm not a double E but was an electrician for 45 years and passed my Master's Test in 1981. I am assuming that the separation requires enough distance that such a fault to a water line should not occur.

However, years ago I had a service call on a swimming pool where the residents were receiving small shocks. I wired the pool and anything I did with pools, hot tubs or saunas was done strictly as per NEC. I don't care who you are, getting shocked around your pool is cause for concern. What we finally found, after a few days and having the utility company out with one of their real engineers is that the spurious current was coming from an underground transformer some 2 or 3 building lots away. IIRC, more grounding was installed at the transformer and I added more grounding at the electrical service to the home and a driven ground at the pool disconnect. Never saw that before or since.

Allow me to explain 'real engineer'. Locally the utilities will call a lot of their field personnel 'engineers' who are no more an engineer than I am. One that always blew my mind was 'staking engineer'. He was the fella who came out and drove stakes where poles, laterals or transformers were to be set. I never knew one to be a 'real engineer' and some made you wonder if they got through high school.