Wouldn't it also need a continuous copper pipe until it meets the ground? A pipe being made of copper or iron doesn't mean it's not connected to a plastic pipe or adapter upstream; and I've seen plumbers using a rubbery-looking tape between the threads when screwing two metal pipes together, which might not be conductive.

I just fixed this situation in a house from the 70s. Cable coax lines grounded to a metal hose bib ... which, in the crawl space, switches to PEX about a foot away from the bib.

Cable guy installing high speed internet was all "nope!". I think the previous owners just had crap internet and didn't ever get into why.

The coax shield must be broken somewhere between you and the service provider. "Grounding" a coax to PEX should never make a difference in any way.

I think part of his worry was lightning strike busting their equipment. Unsure about the rest.

> Wouldn't it also need a continuous copper pipe until it meets the ground? A pipe being made of copper or iron doesn't mean it's not connected to a plastic pipe or adapter upstream

Right.

> I've seen plumbers using a rubbery-looking tape between the threads when screwing two metal pipes together, which might not be conductive

Probably PTFE (teflon) tape.

The thing to do with oldschool copper pipes though was to braze them together, which is conductive.

Water is actually not very conductive at all which is why you need to install ground links if you break into an existing grounded pipe.

And the purpose of grounding the pipe isn't to use the pipe as a ground (some very old electrical setups may have done this), it is to prevent the pipe from getting energized by a wire or something resting against it. If the pipe is properly grounded, that'll short out a breaker.