swimming pool question

[SteveLaorenza]

I got a call for a potential problem with a swimming pool. Customer called me and said that a couple of adults were feeling pins and needles type of sensation when sitting on the pool deck (inground pool/pavers apron around pool) and their feet were in the water. I checked for voltage and I found a half a volt between the water and the pool deck. The pool was installed in 2010 and the only water bond is through the stainless steel ladder. Any suggestions on this? Also,they have a fence on one side, within 5 feet of the water that is not bonded.

 

[James L]

I got a call for a potential problem with a swimming pool. Customer called me and said that a couple of adults were feeling pins and needles type of sensation when sitting on the pool deck (inground pool/pavers apron around pool) and their feet were in the water. I checked for voltage and I found a half a volt between the water and the pool deck. The pool was installed in 2010 and the only water bond is through the stainless steel ladder. Any suggestions on this? Also,they have a fence on one side, within 5 feet of the water that is not bonded.

Is the ladder bonded?
Seems maybe not

 

[Little Bill]

You would need to verify that everything that is supposed to be bonded is bonded. There should be either a grid around the pool or a ring encircling the pool made of bare #8 copper wire. This grid/wire should be bonded to the ladder, pool pump, and any other pool equipment. There are numerous things that could cause this but sounds like either the grid/wire is not bonded to the ladder, or there was no grid/wire installed.

 

[kwired]

You would need to verify that everything that is supposed to be bonded is bonded. There should be either a grid around the pool or a ring encircling the pool made of bare #8 copper wire. This grid/wire should be bonded to the ladder, pool pump, and any other pool equipment. There are numerous things that could cause this but sounds like either the grid/wire is not bonded to the ladder, or there was no grid/wire installed.

simple thing to try first is to make "extension test leads" of some sort and test for voltage between say a ladder in one area and another ladder or other exposed item you know should be bonded. If you do read voltage chances are there is no proper equipotential grounding or at least a portion of it has failed.

 

[Little Bill]

I was going to post Mike Holt's video of how to check the equipotential bonding of a pool but couldn't find it, at least not how it used to be called/listed.

@SteveLaorenza
If you go to www.mikeholt.com then look on the left side for "free stuff", then below that to "videos", then look at the list and find "Swimming Pool Bonding". The video I wanted to post is in video. It is very helpful and informative!

 

[brantmacga]

I’ve seen the lugs in the bottom of the ladder receptacle corrode and break. You’ll need to pull the ladder out to check it.


Sent from my iPhone using Tapatalk

 

[sdbob]

Step 1 would be to dump the main to verify the gradient is coming from the property you think it's coming from. Could very possibly be a neighbor's problem.

 

[sdbob]

Step 1 would be to dump the main to verify the gradient is coming from the property you think it's coming from. Could very possibly be a neighbor's problem.

Visualize 2 services fed from a common transformer.

Service A has a loose neutral on the incoming wires, and as a result is dumping a very small amount of current into the ground via the grounding electrode.

Service B has a swimming pool between it and Service A. It also has a grounding electrode, which helps soak up and route the gradient caused by Service A back to the common transformer windings.

I've seen it.

 

[kwired]

Step 1 would be to dump the main to verify the gradient is coming from the property you think it's coming from. Could very possibly be a neighbor's problem.

Might need to open the service neutral also to verify where it is coming from.

That said if there is proper equipotential bonding it shouldn't matter if the service neutral is sitting there at 2 volts to earth or at 1000 volts to earth, the idea is to put all items around the pool and we kind of don't really care what potential to ground is.

 

[gerald1967]

Might need to open the service neutral also to verify where it is coming from.

That said if there is proper equipotential bonding it shouldn't matter if the service neutral is sitting there at 2 volts to earth or at 1000 volts to earth, the idea is to put all items around the pool and we kind of don't really care what potential to ground is.

We have several pools in our area with voltage coming in on the power co.'s neutral, but one in particular that is worse than the othes. 1.8volts to as much as 4 volts around the pool deck, hot tub, pond out back. everything is bonding and correct. tried adding more ground rods at the service to help pull it down. it only goes away when you clear the utility neutral. owners brother almost got in a fight with him last year, left the house and said he's never bringing his kids back. pool guy was installing the new pool liner last week and quit the job, "not coming back till you fix it"
Power co. power quality technician met me out there clear back in 2011 to document all of the numbers and said "acknowledge it's coming from us, it is not a hazard and we won't be doing anything further". Left several messages with the new power quality technician and can't get him to call me. I agree it's technically not a hazard, the inspector says it is, but it's just enough voltage that it makes everyone nervous. Does anyone have any ideas on this? Thanks in advance. Gerry

 

[Strathead]

What would be the best way to check for equipotential bonding? I am thinking a Millivolt meter, like the Hamden we use for hospital patient rooms, but I would think a good old Wheatstone Bridge would work also.

 

[don_resqcapt19]

We have several pools in our area with voltage coming in on the power co.'s neutral, but one in particular that is worse than the othes. 1.8volts to as much as 4 volts around the pool deck, hot tub, pond out back. everything is bonding and correct. tried adding more ground rods at the service to help pull it down. it only goes away when you clear the utility neutral. owners brother almost got in a fight with him last year, left the house and said he's never bringing his kids back. pool guy was installing the new pool liner last week and quit the job, "not coming back till you fix it"
Power co. power quality technician met me out there clear back in 2011 to document all of the numbers and said "acknowledge it's coming from us, it is not a hazard and we won't be doing anything further". Left several messages with the new power quality technician and can't get him to call me. I agree it's technically not a hazard, the inspector says it is, but it's just enough voltage that it makes everyone nervous. Does anyone have any ideas on this? Thanks in advance. Gerry

Additional connections to the earth never makes the voltage go away...it simply raises the voltage of the earth for a small area around the connection to earth (grounding electrode).

The whole purpose of the required pool bonding is to raise the voltage of the pool water and everything within reach of the pool to match the voltage on the electrical grounding system.

If you are measuring voltage between the pool water and anything close by the pool, you do not have the bonding that is required by the code.

 

[don_resqcapt19]

What would be the best way to check for equipotential bonding? I am thinking a Millivolt meter, like the Hamden we use for hospital patient rooms, but I would think a good old Wheatstone Bridge would work also.

A standard digital meter is fine for the purpose.
Install a remote grounding electrode as far away from the service grounding electrodes and the pool equipment as possible. Ideally 50' or more.
Read the voltage between the service main bonding jumper and the remote grounding electrode. Then read the voltage between all of the pool parts, perimeter areas (putting water on the pool deck helps with this measurement), and water to the remote rod. The numbers should be the same as what was measured between the main bonding jumper and the remote rod. Ideally you would have two people and two meters to compare the voltages at the same time. Changes in loading on the electrical system including on the electrical distribution system will change the voltage between the main bonding jumper and the remote rod.

 

[gerald1967]

A standard digital meter is fine for the purpose.
Install a remote grounding electrode as far away from the service grounding electrodes and the pool equipment as possible. Ideally 50' or more.
Read the voltage between the service main bonding jumper and the remote grounding electrode. Then read the voltage between all of the pool parts, perimeter areas (putting water on the pool deck helps with this measurement), and water to the remote rod. The numbers should be the same as what was measured between the main bonding jumper and the remote rod. Ideally you would have two people and two meters to compare the voltages at the same time. Changes in loading on the electrical system including on the electrical distribution system will change the voltage between the main bonding jumper and the remote rod.

yep did all that multiple times, test rods are 50' plus away from the pool and even at the service where we removed the utility neutral we have 4 volts to the test rods. I actually have the power co tech coming out on friday to confirm all of the measurements again and see what recommendations he'll have. He did mention adding more ground rods at their transformer pole 200' away has helped in the past with other sites, ??

 

[don_resqcapt19]

yep did all that multiple times, test rods are 50' plus away from the pool and even at the service where we removed the utility neutral we have 4 volts to the test rods. I actually have the power co tech coming out on friday to confirm all of the measurements again and see what recommendations he'll have. He did mention adding more ground rods at their transformer pole 200' away has helped in the past with other sites, ??

If you have a voltage from the pool equipment to the remote rod that is different from the voltage between the main bonding jumper and the remote rod, the pool is not properly bonded.

Between what points are you measuring the 4 volts when the utility neutral is disconnected?

The adding of grounding electrodes by the utility can help reduce the neutral to earth voltage on the primary system neutral, but they really need to find the poor connection in their primary neutral system.

 

[gerald1967]

If you have a voltage from the pool equipment to the remote rod that is different from the voltage between the main bonding jumper and the remote rod, the pool is not properly bonded.

Between what points are you measuring the 4 volts when the utility neutral is disconnected?

The adding of grounding electrodes by the utility can help reduce the neutral to earth voltage on the primary system neutral, but they really need to find the poor connection in their primary neutral system.

With the neutral disconnected the voltage exists between their neutral and the remote rods. it goes away at the pool when you disconnect the utility neutral or remove all grounding and bonding at the pool.

 

[don_resqcapt19]

With the neutral disconnected the voltage exists between their neutral and the remote rods. it goes away at the pool when you disconnect the utility neutral or remove all grounding and bonding at the pool.

That is neutral to earth voltage and is really the voltage drop on the utility neutral, and can be a combination of the drops on their primary and secondary neutrals.

Of course it goes away when you disconnect the pool from the electrical system.

The bonding rules result in all of the bonded equipment being raised to the voltage on the neutral at the service disconnect.

Where the bonding is done correctly, everything within touch at the pool is at the same voltage and there is no issue. The elevated neutral voltage only becomes an issue at the pool when there are conductive things that can be touched from in or around the pool that are not at that same voltage.

 

[LarryFine]

Where the bonding is done correctly, everything within touch at the pool is at the same voltage and there is no issue. The elevated neutral voltage only becomes an issue at the pool when there are conductive things that can be touched from in or around the pool that are not at that same voltage.

Exactly right. This points out the difference between bonding and grounding (earthing).

It's likely that the voltage is occurring between bonded and other earthed surfaces.