That apprentice's question about bonding jumped me off yesterday

He asked why we bother with the water pipe bond on a house with PEX and I ended up spending 45 minutes explaining how a metal water main can still energize through the street side, which made me realize I should teach these basics more often instead of just doing them.

3 comments

3 Comments

evan_green5220h ago

Respectfully, I see this a bit different. That street side water main can absolutely bring voltage onto the property even with PEX inside, but the bond isn't really about keeping the pipe at ground potential. The real point of the bond is to give fault current a clear path back to the source so the breaker trips. If you depend on the water main as your only ground, you're banking on the street side connection being good, which it often isn't. I've seen plenty of old meter set ups with rubber gaskets or plastic fittings that break that path entirely. That's exactly why we drive ground rods and bond everything back to the panel. The bond helps, but it's the rod and the service neutral that actually do the heavy lifting.

laura_schmidt8215h ago

Mike Holt actually covered this in a code seminar I watched, showing how broken street side bonds cause shocks even with modern PEX.

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the_alice23h ago

Oh, I see what you're getting at, but there's a small thing I'd gently push back on. In my experience, the water main on the street side can still carry voltage even with PEX inside the house, but the real risk is if there's any metal piping between the meter and the ground rod. That's where the bond actually does its job, keeping everything at the same potential. Just something to keep in mind next time you walk through it with the apprentice.