plumber says not to run water line in attic?

hamsterDecember 29, 2007

Hi all..tearing out bathroom to the stud walls and the ceiling. I want to put in a rain shower head in the ceiling of the shower. The plumber says not a good idea as the pipes may freeze. I live in Minnesota. The attic is insulated. I can't quite understand this. If the pipes are running just above the ceiling and the ceiling is insulated, why would they freeze? If it gets that cold...wouldn't my ceiling have frost on it? Anyone have this type of setup? He pretty much burst my bubble!! Any suggestions?

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mongoct

Your plumber is playing it safe, and there's nothing wrong with that.

If you're running a short section of horizontal across the ceiling, to get from the supply valve wall to the location of the shower head, then do two things:

1) Pitch the horizontal run downwards towards the shower head. That way when the water is turned off, water in the horizontal run should drain out of the tubing.

2) Insulate that horizontal run with rigid foam insulation. I use polyisocyanurate which is R7 per inch. I get 4' by 8' sheets and cut pieces and then assemble them using canned foam for the glue and duct tape to hold it together while the canned foam is curing. Assemble them to form and inverted "U", with the open part of the inverted U against the attic side of the drywall that makes up your showers' ceiling. Run a bead of canned foam to stick the U to the drywall.

You can then replace your existing attic insulation over the inverted U for more freeze protection.

You could also transition that run from copper to PEX, which is cross linked polylethylene. Should that horizontal run not drain and the water within freeze, PEX can survive freeze/thaw cycles better than copper.

Regardless of the material used, strap the horizontal run to a 2x4 or something similar so it doesn't sag over time, allowing it to collect water.

Mongo

    Bookmark   December 29, 2007 at 1:08PM
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hamster

You're the man Mongo! I'll run this past him and see what he has to say. The horizontal would be about 2 feet. Thanks!

    Bookmark   December 30, 2007 at 12:01AM
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mongoct

For 2', stick with copper, pitch it downward, and insulate.

Happy New Year!

    Bookmark   December 30, 2007 at 12:11AM
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toadangel

hey Mongo - thanks for the specific details.

we are doing this same thing, in Ohio, but my friend has been using CPVC pipe for the supplies, not copper. he already has a CPVC line running from the mixing valve up into the attic, & the shower is kerdi'd so we can't change that very easily unless we go through the back wall.
our horizontal run in the ceiling/attic will be about 2' as well - should we switch to pex or copper for the remainder of the run, or would cpvc be ok with your insulated box?

thanks,
lisa

    Bookmark   January 8, 2008 at 10:20AM
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mongoct

Of the three choices, CVPC, Cu, and PEX, CPVC would be my last choice for water supply, especially in a possible freeze/thaw environment.

That said, with the horizontal run being pitched downwards and the shower head able to freely drain, as long as the horizontal run has no dips in it it should not end up with standing water when the shower valve is shut off.

Fully supported PEX has better freeze protection than copper. But copper has better resistance to sagging. Use either as you see fit. It'll probably be easier for you to get a few feet of copper than a few feet of PEX.

If it matters, in my own house (which I plumbed myself) I used Cu, and I had both materials available.

Do be careful with the CPVC if you have any female threaded CPVC couplings. They will be the weakest link in the system in terms of potential cracking.

Mongo

    Bookmark   January 9, 2008 at 12:59AM
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toadangel

thanks mongo - i'm glad looking back that i picked out the connectors we used that had female threads. i chose the ones that had brass female threads & my friend later said i could have saved a buck or two by getting the all-cpvc fittings... glad i didn't.

the cpvc seems to be the standard in my house, and was used in the shower head supply i removed when we started this project. i'll talk to my friend about the issues with the attic, though.

thanks,
lisa

    Bookmark   January 9, 2008 at 8:56AM
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