# Pool Shell Bonding, Conductive and Nonconductive Shells

#### Lmeagles36

##### Member
I do not have a super strong electrical background but I can easily understand electrical theories. One thing I don't understand at least in theory, is why the NEC requires a conductive pool shell to be bonded. Since there has to be a required 9 sq in. water bond anyways, won't the equipotential bonding be accomplished by that since the water is in constant contact with the conductive shell?? Or maybe it would be easier for me to understand the flip side of the theory of why a nonconductive pool shell isn't required to be bonded to the perimeter bonding but a conductive shell is. All of the other bonding requirements for pools makes complete sense to me except for the shell requirement sections for conductive and nonconductive pools.

Can anyone help me understand the reasoning to this?

#### Dennis Alwon

##### Moderator
Staff member
The 9 in sq bonding of the water may keep the water from being energized but the conductive shell would not be protected because the water, even with the chemicals, is not enough to bond the shell thru concrete, etc.

The equipotential bonding of the shell will keep stray voltage at the same potential as the pool. Trying to bond another part of the pool thru water will not do the job.

#### iwire

##### Moderator
Staff member
Can anyone help me understand the reasoning to this?
Dennis nailed it, it would take very little difference of potential between the water the shell to become dangerous to swimmers.

#### Lmeagles36

##### Member
Thank you Dennis. Can you explain to me in theory if people are swimming in a pool and are not in contact with any metal parts or a grounded surface (AKA standing on a vinyl liner). If current accidentally makes contact with the pool water, will the current more then likely find its way back to ground through the human body or only around the human body? I would like to know if basic pool water is more or less resistive than the average human body in a pool?

#### Dennis Alwon

##### Moderator
Staff member
Vinyl liners are considered non conductive shells. You said conductive shell

(1) Conductive Pool Shells. Bonding to conductive pool
shells shall be provided as specified in 680.26(B)(1)(a) or
(B)(1)(b). Poured concrete, pneumatically applied or
sprayed concrete, and concrete block with painted or plastered
coatings shall all be considered conductive materials
due to water permeability and porosity. Vinyl liners and
fiberglass composite shells shall be considered to be nonconductive
materials.

#### Lmeagles36

##### Member
Sorry, I meant if the shell was non conductive such as a vinyl liner, would current return to ground through a human body or simply go around them if the pool water is less resistive?

#### don_resqcapt19

##### Moderator
Staff member
Thank you Dennis. Can you explain to me in theory if people are swimming in a pool and are not in contact with any metal parts or a grounded surface (AKA standing on a vinyl liner). If current accidentally makes contact with the pool water, will the current more then likely find its way back to ground through the human body or only around the human body? I would like to know if basic pool water is more or less resistive than the average human body in a pool?

The wet body is much more conductive than the pool water. The person's body will "short out" the water for the length of the body and more current will flow on or through the body. If you have a salt water pool the opposite is true.

#### Lmeagles36

##### Member
Thanks Dennis for the input, very good info to know.
One question that has been asked to me multiple times is about requiring a perimeter bond for an above ground pool.
Since the NEC claims an above ground pool that can hold water deeper than 42" is considered permanent, and permanent pools require perimeter bonding, does the average above ground pool require a #8 bare solid copper bond wire buried around the perimeter? This is something I have never seen or heard of someone doing on any above ground pool installation.

#### mgookin

##### Senior Member
Hello Lmeagles36 and welcome to the forums.

There's a very informative page by Mike Holt on swimming pool bonding at http://www.mikeholt.com/swimmingpoolbonding.php..

Mike Holt also has some really good material on Grounding and Bonding which you can find on his website.

#### Dennis Alwon

##### Moderator
Staff member
Thanks Dennis for the input, very good info to know.
One question that has been asked to me multiple times is about requiring a perimeter bond for an above ground pool.
Since the NEC claims an above ground pool that can hold water deeper than 42" is considered permanent, and permanent pools require perimeter bonding, does the average above ground pool require a #8 bare solid copper bond wire buried around the perimeter? This is something I have never seen or heard of someone doing on any above ground pool installation.

I cannot say what is common place but yes, an above ground pool that is deeper than 42" does need the perimeter bonding.

#### Dennis Alwon

##### Moderator
Staff member
I cannot say what is common place but yes, an above ground pool that is deeper than 42" does need the perimeter bonding.

The question I have is why is an above ground pool less than 42" treated differently. You can still have stray voltages etc

#### iwire

##### Moderator
Staff member
The question I have is why is an above ground pool less than 42" treated differently. You can still have stray voltages etc
For sure that is true but I think perhaps they had to make a cut off point due to the large numbers of portable pools now on the market.

If they make the codes too restrictive they won't be adopted or just be totally ignored.

I have a pretty large portable pool with filter and I kill the power to it when we use it. When my kids would visit friends with these pools I always worried about how they where powered.

#### Lmeagles36

##### Member
The last question I struggle with for pool bonding and the NEC requirements is bonding for pools that contain structural steel but also have a vinyl liner.

NEC 680.26 B(1) states: Vinyl liners shall be considered to be nonconductive materials.
680.26 B (2) states: Perimeter bonding shall be attached to pool reinforcing steel at 4 evenly spaced points around the pool perimeter, for nonconductive pools shells, bonding at 4 points shall NOT be required. The commentary goes on to say connection between the perimeter bonding and nonconductive shells is not required at all.
Then 680.26 B (3) states: All metallic parts of the pool structure, including reinforcing metal not addressed in B(1) , shall be bonded.

This just seems to me as conflicting sections. The majority (not all) of pools whether above ground or below, contain a vinyl liner with either rebar in concrete, or structural steel studs such as an above ground pool. Must the steel be bonded to the perimeter bonding at 4 points, 1 point, or no points since it is isolated with a vinyl liner???

#### Dennis Alwon

##### Moderator
Staff member
I don't see it as conflicting at all. It essentially states all metal parts must be bonded except the rebar in a vinyl liner.

#### Lmeagles36

##### Member
Understood, but to answer my question: does the structural steel have to be bonded if there is a vinyl liner over it because in one section the NEC says it does not since vinyl liners are nonconductive. Then in another section the NEC says are structural steel needs to be bonded no matter what. That's why I mentioned conflicting sections. It can be argued both ways depending on which NEC referenced section you want to use.

#### Dennis Alwon

##### Moderator
Staff member
Understood, but to answer my question: does the structural steel have to be bonded if there is a vinyl liner over it because in one section the NEC says it does not since vinyl liners are nonconductive. Then in another section the NEC says are structural steel needs to be bonded no matter what. That's why I mentioned conflicting sections. It can be argued both ways depending on which NEC referenced section you want to use.

except the rebar in a vinyl liner.
IOW-- no I don't believe the rebar needs bonding with a vinyl liner over it. I would probably do it anyway in case someone decided to change from a vinyl to concrete pool

#### david

##### Senior Member
The last question I struggle with for pool bonding and the NEC requirements is bonding for pools that contain structural steel but also have a vinyl liner.

NEC 680.26 B(1) states: Vinyl liners shall be considered to be nonconductive materials.
680.26 B (2) states: Perimeter bonding shall be attached to pool reinforcing steel at 4 evenly spaced points around the pool perimeter, for nonconductive pools shells, bonding at 4 points shall NOT be required. The commentary goes on to say connection between the perimeter bonding and nonconductive shells is not required at all.
Then 680.26 B (3) states: All metallic parts of the pool structure, including reinforcing metal not addressed in B(1) , shall be bonded.

This just seems to me as conflicting sections. The majority (not all) of pools whether above ground or below, contain a vinyl liner with either rebar in concrete, or structural steel studs such as an above ground pool. Must the steel be bonded to the perimeter bonding at 4 points, 1 point, or no points since it is isolated with a vinyl liner???
Just because an above ground pool has a vinyl liner does not mean that the alum / composite metal support post with in 5 ft. of the pool water does not require a bond to the bonding system.

I commonly run into multiple situations with combination of non conductive and conductive materials with above ground pools

#### Lmeagles36

##### Member
Can anyone explain in theory about the pool surface bonding method of a #8 bare copper, 18"-24" away from pool wall and buried 4"-6" deep.

As I have seen several of these bonding systems up close in person, it seems to me as 1 single conductor buried under 4"-6" of loose fill would not likely provide good conductivity to a human's body (feet) to balance out the potential of when someone is standing on the perimeter surface and touching the pool water.

Wouldn't it be much better conductivity and much less chance of potential differences to just require a concrete surface around every pool and call it done?
I'm just trying to understand of how the NEC came up with (1) #8 wire, at 4"-6" in depth and 18"-24" away.

Thoughts??

#### Dennis Alwon

##### Moderator
Staff member
Can anyone explain in theory about the pool surface bonding method of a #8 bare copper, 18"-24" away from pool wall and buried 4"-6" deep.

As I have seen several of these bonding systems up close in person, it seems to me as 1 single conductor buried under 4"-6" of loose fill would not likely provide good conductivity to a human's body (feet) to balance out the potential of when someone is standing on the perimeter surface and touching the pool water.

Wouldn't it be much better conductivity and much less chance of potential differences to just require a concrete surface around every pool and call it done?
I'm just trying to understand of how the NEC came up with (1) #8 wire, at 4"-6" in depth and 18"-24" away.

Thoughts??
I don't know if I can explain in theory but basically the perimeter bonding takes any voltage that may have leaked into the earth from power company or some underground lines and keeps the pool area at the same potential.

For instance , if there is a 2 volt leakage in the earth then everything associated with the pool is also at 2Volts thus no shock is possible