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Testing a Swimming Pool Bonding Grid

Pool Design article by Paolo Benedetti

Required tools

  • An analog ohmmeter (meter with a needle, not digital). Available at Home Depot for $10
  • A roll of wire (long enough to reach from the pool equipment pad to the furthest point to be tested)
  • Alligator clamps (attached to each end of the roll of wire)

Testing Procedure

STEP 1 - "Zero out" (calibrate) the meter:

Attach one of the ohmmeter leads to an alligator clamp that is on one end of the wire. Attach the other alligator clamp to the other ohmmeter lead. The meter will display a measurement (it is measuring the resistance of the roll of wire). Use the calibration dial to return the needle to zero. You are now ready to start.

STEP 2 - Testing

Disconnect one alligator clip from the meter and attach it to an exposed bonding at the equipment pad. Use the probe without the alligator clip to take readings of various metallic components, but touching it to them. The needle should remain close to zero. If you are using the 10X scale, multiply reading by 10 to get the true Ohms.

The following items should read zero ohms of resistance

  • Pool Heater
  • Pool Pumps
  • Any piece of pool equipment that is metal Pool Controller (or time clock box)
  • Related circuit panels
  • The internal grounding bar of all pool light junction boxes
  • The external bonding lug of the light junction box
  • The metal parts of the diving board, slide, deck anchors, umbrella sleeve, fountain heads, spillways, waterfalls, etc.
  • Anything containing over 4 square inches of metal that is within 5 feet of the pool (in any direction): downspouts, hand railings, steel in the pool deck concrete, window frames, metal skimmer lids & drains, pool cover tracks, lids; HVAC venting, sheet metal, directional louvers; metal framing or foundation reinforcing steel of an enclosure building, etc.
  • Swimming pool light niches can only be tested with the water removed from the pool. When installed, the stainless steel (SS) light fixture's face ring should read zero. The SS straps inside of a plastic light niche and body of a SS niche should also read zero.

If these components show a resistance other than ZERO, then their bonding is corrupt. It means that the continuity is broken or there is a poor connection somewhere.

Paolo Benedetti

Paolo Benedetti

Aquatic Technology Pool & Spa
PO Box 130
Morgan Hill, CA 95023
T (408) 776-8220