5 mistakes to avoid when bonding a swimming pool

Pool bonding is where careless work gets people killed. The equipotential bonding grid in NEC 680.26 exists because voltage gradients in wet environments do not forgive shortcuts. Inspectors fail more pools for bonding errors than almost anything else in Article 680. Here are the five mistakes that keep showing up on callbacks and red tags.

1. Treating the bonding grid as a grounding conductor

The equipotential bonding grid required by NEC 680.26(B) is not a grounding electrode and it is not an equipment grounding conductor. Its job is to keep every conductive surface a swimmer can touch at the same potential, so current does not flow through a body bridging two points.

You do not run the #8 solid copper back to the panel ground bar to satisfy 680.26. You bond the grid together, then you connect it to the equipment that needs bonding. The equipment grounding conductors run separately through the branch circuit wiring per 680.23 or 680.24.

If you find yourself pulling the bonding conductor through conduit back to the service, stop. You are confusing 250.118 with 680.26. They are different systems doing different jobs.

2. Skipping the perimeter surface bond

NEC 680.26(B)(2) requires bonding of the perimeter surface extending three feet horizontally beyond the inside walls of the pool. This is the part guys forget on existing pools or on jobs where the deck is poured before the electrician shows up.

The code gives you two options for the perimeter: structural reinforcing steel that is bonded together, or a #8 solid bare copper conductor. The copper has to follow the contour of the perimeter, sit between 18 and 24 inches from the inside wall, and be buried 4 to 6 inches below the subgrade.

• #8 AWG solid bare copper minimum
• 18 to 24 inches from the inside pool wall
• 4 to 6 inches below subgrade
• Bonded to the grid at a minimum of four points, evenly spaced

If the deck is already poured and there is no rebar tied in, you are looking at a copper ring buried around the perimeter or a serious conversation with the pool contractor.

3. Missing the metallic parts list under 680.26(B)

The list in 680.26(B)(1) through (B)(7) is not optional reading. Every metallic component within five feet of the inside walls of the pool, or that could become energized, gets bonded. Electricians routinely miss the less obvious items.

Things that get forgotten:

• Metal fittings within or attached to the pool structure (ladders, handrails, diving board anchors)
• Metal parts of electrical equipment associated with pool water circulating systems, including pump motors
• Metal raceways and metal piping within five feet of the inside walls
• Metal awnings, fences, and door frames within five feet that are not separated by a permanent barrier
• Pool covers with electric motors

Double insulated pump motors per 680.26(B)(6)(b) get a solid #8 left accessible at the motor location for future replacement. Do not cut it short. The next guy needs it.

4. Using the wrong connectors or the wrong material

NEC 680.26(B) requires bonding conductors to be solid copper, insulated covered or bare, and not smaller than #8 AWG. Stranded does not satisfy the rule for the grid conductor itself. The connections have to be listed for the purpose and listed for direct burial where applicable, per 250.8 and 680.26(B).

Common failures on inspection:

1. Stranded #8 used for the grid (not permitted)
2. Split bolts or wire nuts used in direct burial locations
3. Brass lugs on aluminum equipment without listed transition
4. Exothermic welds that are not actually fused (cold weld)
5. Pressure connectors not listed for direct burial buried anyway

If a connector is not stamped DB or listed for direct burial in the manufacturer instructions, it does not go in the dirt. Inspectors check this. So should you.

5. Forgetting the pool water itself

NEC 680.26(C) requires the pool water to be intentionally bonded with a minimum conductive surface area of nine square inches in contact with the water, electrically connected to the equipotential bonding grid. People miss this constantly on vinyl liner pools and fiberglass pools where there is no metallic shell touching the water.

If your pool has a wet niche metal light, metal ladder cup anchors that contact water, or a metal skimmer in contact with water, you may already meet the nine square inch requirement. Verify it. Measure it. Do not assume.

If you do not meet it, install a listed water bond fitting. They are inexpensive, they thread into the circulation plumbing, and they connect to your bonding grid with the same #8 solid copper. Skipping this is a clean inspection failure.

Field checklist before you call for inspection

Walk the pool one more time before the inspector shows up. The grid is buried, so you need to confirm it on paper and with photos taken during installation.

• Photos of rebar ties or perimeter copper before the pour
• All bonding lugs visible and tight on pump, heater, and light niche
• #8 solid left accessible at any double insulated motor
• Water bond fitting installed or metallic water contact verified at nine square inches
• All metal within five feet documented and bonded
• Connectors listed for the location they are installed in

Bonding is not the place to save fifteen minutes. The grid is the last line of defense between a fault and a swimmer, and 680.26 spells out exactly what it has to look like. Build it that way the first time.