Pool bond question. Potential difference

[Mystic Pools]

The deck was tore up. There was no obvious bond, so they chipped into the old pool shell to get to rebar and installed 4 stingers. Installed a bond loop and tied it all together. Wet niche lights are a thing of the past and new lights are not bonded anymore. Water bonds are the rebar in concrete pools.

Were the 4 rebar points verified for continuity? Prior to running perimeter bond?
Wet niche lights are still used a lot. Thet have not disappeared.

I have not used a wet niche for new builds in over 20 years. Even on renos I remove original wet niche lights and use the nicheless lights, which is what you are referring to. Yes, no bonding or grounding on them.

A water bond is required for all pool types as Little Bill noted per 680

 

[electricblue]

That's not correct. Anything bonding the water has to be in direct contact with the water.

(C) Pool Water. Where none of the bonded parts is in direct
connection with the pool water, the pool water shall be in
direct contact with an approved corrosion-resistant conductive
surface that exposes not less than 5800 mm2 (9 in.2) of surface
area to the pool water at all times. The conductive surface shall
be located where it is not exposed to physical damage or
dislodgement during usual pool activities, and it shall be
bonded in accordance with 680.26(B).

From the NFPA:
Where bonded items such as ladders, rails, or underwater luminaires are in direct contact with the pool water and provide the required surface area, it is not necessary to provide another conductive element. A conductive pool shell in contact with the water also satisfies this requirement. However, where the pool does not include any of those items, it is necessary to install a conductive element, such as the type illustrated below within a pool's water filter. These devices have been specifically listed as a means to provide this contact with the pool water.

 

[retirede]

From the NFPA:
Where bonded items such as ladders, rails, or underwater luminaires are in direct contact with the pool water and provide the required surface area, it is not necessary to provide another conductive element. A conductive pool shell in contact with the water also satisfies this requirement. However, where the pool does not include any of those items, it is necessary to install a conductive element, such as the type illustrated below within a pool's water filter. These devices have been specifically listed as a means to provide this contact with the pool water.

How does that apply to this installation? He only bonded the rebar in the deck.

 

[Ponchik]

How did you measure the voltage, and could it have been a DC measurement?

Is the voltage present with power off?

Are there different equipment terminals ( eg. pool and spa pumps) where you can take a resistance measurement?

Where would the DC voltage be coming from?

 

[winnie]

Where would the DC voltage be coming from?

The OP reported less than 0.668V. That could come from a parasitic electrochemical cell formed by dissimilar metals in contact with pool water.

Not relevant since they got an AC measurement.

 

[Ponchik]

The OP reported less than 0.668V. That could come from a parasitic electrochemical cell formed by dissimilar metals in contact with pool water.

Not relevant since they got an AC measurement.

If it was a DC voltage from dissimilar metals, will cause a tingling shock feeling?

 

[winnie]

If it was a DC voltage from dissimilar metals, will cause a tingling shock feeling?

9V DC to the tongue certainly causes a shocky feeling. I don't know about 0.7V DC to wet skin. I'm not enough of a connoisseur to describe the difference between DC and AC low voltage shocks.