PEX to a guest house. do I need a copper riser?

[Zimm0who0net]

I've got a 1-1/4" PEX line coming from my main house to a guest house (it's after the main shutoff). It obviously needs to surface through the slab and into the guest house. My drafter tells me to surface outside the guest house with copper, go through a shutoff valve, and then through the wall into the guest house where I can transition back to PEX.

My question #1: If PEX can run underground, above-ground, and through a slab (protected), why do I need copper at all? Can't I just surface inside the structure with PEX and go from there?
Question #2: The line running from the main house to the guest house has a specific shutoff for that length already. Do I need an additional shutoff AT the guest house? If so, is there any reason I wouldn't put that shutoff inside the structure? (here in southern AZ almost every water shutoff I've seen has been outside the structure, but that seems silly to me given that we DO occasionally have freezes)

 

[Terry]

You can check with a local plumbing inspector, but I doubt there is any need for copper.
Personally I would have a shutoff for the guest house in an accessible location. In the Seattle area, we put those inside because of freezing.

Your electrical panel should have it's own grounding. For those with homes built in the 70's and 80's, they often used five feet of copper on the incoming water for grounding on the panel. When homes were repiped, the panel needed grounding before the water line was cut. Some bad things happened to plumbers when the correct steps weren't taken.

 

[Sponsor]

 

[Zimm0who0net]

Thanks Terry. That's what I thought. I'll probably surface inside the house with PEX and then immediately go into a ball valve shutoff.

I'm totally familiar with the grounding issue as I just recently repiped a main line with PEX for an old 1955 house with galvanized that finally gave up after 70 years. Had to run a couple ground rods as part of that project because the old galvanized was going away.

The guest house is all new construction, so it'll have its own UFER ground.

 

[Plumber69]

You can check with a local plumbing inspector, but I doubt there is any need for copper.
Personally I would have a shutoff for the guest house in an accessible location. In the Seattle area, we put those inside because of freezing.

Your electrical panel should have it's own grounding. For those with homes built in the 70's and 80's, they often used five feet of copper on the incoming water for grounding on the panel. When homes were repiped, the panel needed grounding before the water line was cut. Some bad things happened to plumbers when the correct steps weren't taken.

I still use copper, but I know people using pex now, 95% of houses here are grounded by the water line. What bad things happened?

 

[wwhitney]

Bad thing happen when you open up a conductor carrying current, particularly if you are in contact with one or both ends of the conductor. And with a metallic water service, there is almost always electrical current on the water service:

If two neighboring houses both have metallic water services, then standard electrical practice is that at each house the water service is used as a grounding electrode, and the water service ends up connected to the electrical service neutral via the electrical services's neutral-ground bond.

So that means under normal working conditions there will usually be neutral current present on the water service: whichever house has a greater neutral current at the moment, that excess neutral current can either travel back via the electrical service neutral, or via the water service to the neighbor's water service and the neighbor's electrical service neutral. Current will take all paths available in relation to their resistances, so some current will be on the water service.

Worst is if one of the two houses' electrical service neutral conductor fails. Then all of that house's neutral current will return via the neighbor's (or multiple neighbors') water service and electrical service neutral conductor. The water service is often such a good conductor that the failed neutral conductor will go unnoticed for years.

Cheers, Wayne

 

[Highlander]

He’s probably suggesting copper for the outside riser because PEX is sensitive to exposure to UV/sunlight.