Why bother with the water pipe?

[Ponchik]

When we use the water pipe as an electrode, we have not inspected the condition of the pipe and we are assuming the following:

It is in a good shape, not rusted, it is metal and has at least 10' of contact with the soil. What if the our assumption is not correct.

What i am getting at is, unless we can verify that the water pipe is metal, has 10' of soil contact and is in a good shape, lets forget about using the water pipe as an electrode and just install two ground rods and call it a day.

anyone else agree with me?

 

[infinity]

If 10' of buried water pipe is present at the structure it must be used as an electrode. It also requires supplementation by at least one additional electrode. Since many buried metallic water pipes are copper it might be reasonable to assume that it's at least 10' long if in an existing building. Even if it were made of another material such as steel I think that if it were corroded someone would notice. :roll:

 

[Dennis Alwon]

It does not hurt to use the water pipe as an electrode. Because these pipes often get replaced with plastic, I believe, that is the reason we need to supplement the water pipes with ground rods.

 

[Ponchik]

I agree and understand that if there is metallic water pipe to the building it has to be one of the electrodes and has to be supplemented with an additional electrode.

But my questions is why even bother with the water pipe. Since the water pipe is underground and sometimes been there for years why do we have to assume that it is in a good shape, has good contact with the earth, it is not plastic, and it is not rusted.

Why can't we just install our own electrodes and not assume anything on the water pipe.

 

[Ponchik]

Even if it were made of another material such as steel I think that if it were corroded someone would notice. :roll:

You will probably agree that there are old galvanized pipes that are corroded on the outside but yet don't leak water. They are good for water but not good as an electrode.
Besides if the pipe is underground it is hard to notice.

 

[infinity]

You will probably agree that there are old galvanized pipes that are corroded on the outside but yet don't leak water. They are good for water but not good as an electrode.
Besides if the pipe is underground it is hard to notice.

IMO if a pipe can still carry pressurized water without leaking it's probably better than a ground rod as an electrode.

 

[LarryFine]

What i am getting at is, unless we can verify that the water pipe is metal, has 10' of soil contact and is in a good shape, lets forget about using the water pipe as an electrode and just install two ground rods and call it a day.

anyone else agree with me?

Not quite. Whether it qualifies as an electrode or not, it's still a good idea for a metallic water pipe system to be bonded.

 

[gar]

110408-2227 EDT

Edward:

Have you ever measured the resistance of a corroded galvanized water pipe to earth to determine that because it is corroded that it makes a poor earth connection.

A corroded metallic water pipe extending to the street is almost certainly a better ground connection than the combination of two 8 or 10 ft vertical ground rods. The surface area is almost certainly much greater. The surface area of the electrode and the nature of the soil will determine the resistance to earth. Not all of the galvanize will be lost and the various oxides of iron are reasonably good electrical conductors.

In my case I have 150 ft of 1" copper at least 8' below grade for my water line and it is the only ground electrode. When the house was built ground rods were not required to supplement the water line.

In general for reliability and other reasons given above it makes logical sense to use the combination of the metalic water pipe and driven ground rods as the means of earthing the system. Whether you call the water pipe or the driven rods the ground electrode, and the other as supplemental makes no difference. The whole combination is the ground electrode. The more stuff you put in the ground outside of the house and the lower the high frequency impedance to connect to this stuff the better protected you will be in a lightning storm.

What does not make sense is to have the service entrance and water line enter the building in different locations, and bond them together. It does not make sense to put a supplemental ground rod into the earth somewhere inside the building far from the main earthing point which is required to be near the main panel. What you do not want is lightning current to flow to different grounding points within the building. Keep the lightning current outside of the building. Thus the design of the building should be to put the water supply to the building at the location of the main panel.

.

 

[mh183]

doesn't the fact that it is charged with water which conducts electricity make this a good ground and another question with keeping in mind a fully charged line do we put a jumper at the water meter

 

[gar]

110409-0858 EDT

mh183:

Water in a 1/2 or 3/4 metal pipe is a very poor conductor of electricity, even with a very high salt concentration, in comparison with the pipe itself. The pipe could leak like a sieve and be a better conductor than the water.

.

 

[mh183]

ok i see ur point what about the jumper at the water meter

 

[gar]

110409-0943 EDT

mh183:

The water meter jumper is to insure a low impedance from the outside supply pipe to the interior piping system. However, once you go to plastic pipe the use of the water system as a grounding system is lost.

.

 

[boboelectric]

I will agree. 2 grounding rods,water line g.e.c. , Also bond h to c water pipes at water heater .They used 2" green pipe when I got city water.

 

[ptonsparky]

Even is systems that are working properly the best way to avoid that "tingling sensation" while in the shower is to bond the water line. In communities with common metalic water lines there will be current flowing on the pipes. If you have current, you have potential.

 

[mark32]

110408-2227 EDT

What does not make sense is to have the service entrance and water line enter the building in different locations, and bond them together. It does not make sense to put a supplemental ground rod into the earth somewhere inside the building far from the main earthing point which is required to be near the main panel. What you do not want is lightning current to flow to different grounding points within the building. Keep the lightning current outside of the building. Thus the design of the building should be to put the water supply to the building at the location of the main panel.

.

Hello Gar,

Last year I wired a detached structure for an acquaintance, existing was a pedestal mounted sub panel roughly 10' away from the structure (Which feeds pool pumps etc). When the structure was built the ec installed pvc underground and into the structure to feed the structure's panel. At first I was going to take the gec from the outdoor panel and run it over to the ground rods but the panel was so full I would have had to add a lug or additional ground bar so I took the gec from the indoor panel. The total length of that gec inside is probably around 20'. Was that a bad idea? If need be I could always disconnect it when I go back to finish and redo it as I had initially intended.

 

[gar]

110413-1259 EDT

mark32:

You need to address your question to the code guys.

I did not really follow your description, but with a pool involved you need to be very careful that no undesired current flows in and around the pool.

Apparently you have a house, a detached pool, a detached building, a sub-panel in the yard, and pool pumps somewhere. There is a least one PVC underground from the house to one or more places. These places are the yard sub-panel, and the detached building. Not clear if there are one or two conduits from the house. If it is one conduit, then does it run to the outside sub-panel first or to the outbuilding?

Have to assume there is a proper grounding setup at the house. Where else are there any ground rods, and how are these related to the EGC, and/or neutral? What is done to prevent a potential difference between the pool water and any surrounding earth or objects?

Have you made any high impedance voltmeter readings between the pool water, the earth, and surrounding objects?

.

 

[mark32]

Hello Gar, thanks for your response.

There is one conduit that runs from the house to the pedestal mounted sub panel, from there it feeds the detached structure. The pedestal mounted sub feds two pool pumps which are in the immediate vicinity, the pool itself is roughly 70' from this location. The detached structure is at most 10' away from this outdoor sub and the ground rods are driven next to the structure. The neutral and egc's are isolated in both subs and the gec taken from inside the structure is taken from the equipment grounding bar, of course. Everything was in place when I showed up, the pool and associated equipment had been inspected before I showed up, not sure what type of equipotential bonding is in place. I did not take any measurements. The detached structure had been inspected so the inspector must have seen the rods.

 

[PetrosA]

I'm pretty sure bonding water meters serves a purely safety related function rather than an impedance one. When I started in residential back in the 80s many of the houses didn't have the water meters bonded yet and plumbers and water company personnel would get electrocuted if they happened to pull the meter when there were neutral issues.

 

[Ponchik]

I'm pretty sure bonding water meters serves a purely safety related function rather than an impedance one. When I started in residential back in the 80s many of the houses didn't have the water meters bonded yet and plumbers and water company personnel would get electrocuted if they happened to pull the meter when there were neutral issues.

It will still happen. If there is a lose or disconnected neutral those electron have to get back to source somehow.

 

[e57]

It does not hurt to use the water pipe as an electrode. Because these pipes often get replaced with plastic, I believe, that is the reason we need to supplement the water pipes with ground rods.

Apparently in an other thread up right now - the supplemental rods pre-date use of plastic piping????

Not quite. Whether it qualifies as an electrode or not, it's still a good idea for a metallic water pipe system to be bonded.

Agreed - more on that in a moment.

I'm pretty sure bonding water meters serves a purely safety related function rather than an impedance one. When I started in residential back in the 80s many of the houses didn't have the water meters bonded yet and plumbers and water company personnel would get electrocuted if they happened to pull the meter when there were neutral issues.

This is where it gets into the aether - many older water meters I see - were never bonded across them - galvy to brass/bronze - then copper brazed to bronze, the older ones lacked dielectric fittings. - If say - every house on the block were bonded to/grounded by the water pipe - it WOULD carry neutral current, and most likely save the house from a possibly terrible fire. There are a number of white papers on the topic of plumbers getting shocked, and the gas industry recently going hog wild about bonding gas lines - making the gas lines a de-facto electro system, or carrying current like this to other building in the case of a lost neutral - or carrying parallel current.

Personally I think it has saved more lives than one would think - apart from plumbers who would differ... But most experience plumbers know the hazard. Some use jumper cables...

Some time ago - I got a call from an angry client dead set on suing the plumber working on the house next door - for destroying his TV/computer or what ever it was. Took some time to educate the guy that it was his NEUTRAL that failed. Breaking the main water line on the house next door only alerted to a problem that may have existed for years - IN HIS OWN home - and not the fault of the plumber.