Why 2 hot and 2 cold pipes out of slab?

Old 05-19-03, 10:05 PM
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Why 2 hot and 2 cold pipes out of slab?

I am remodelling my bathroom and don't understand why it is plumbed the way it is now. Both the hot and cold water supply lines come out of the slab with 2 pipes that are joined together (using a T) approximately 6-8" above the slab. (A total of 4 pipes emerge from the slab - 2 for hot and 2 for cold.) This is true for both the sink and the shower.

Here's the reason I need to understand... I am moving the shower supply lines approximately 3 feet from one wall (ex-wall actually - I wasn't fond of it) into another wall... Do I need to carry the dual-piping all the way across under the slab and then up in the new location so they are joined above the slab like they are now? Can I just bend the pipes like they are now over under the slab and run a single hot and single cold the rest of the way to the new location (this would have the dual pipes joining into a single beneath the slab approximately 30 inches from where they will emerge).

Please help a confused do-it-yourselfer.

Thanks - John
Old 05-19-03, 10:53 PM
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It is unusual, but someone must have double-plumbed the supply lines in the slab.
Are you on a well or is the public water pressure low? They may have done it for volume or so that one could be capped off if one ever leaked, and the other could carry the supply without having to break into the slab (an expensive proposition).
Whatever the case, I assume that this is 1/2" copper.
If it were me, I would carry the lines double just as they're plumbed now over to the new location.
Don't try to "bend" the lines. Cut them and plumb them properly in the slab.
If you decide to go with one line instead, I would increase the consolidated line size to at least 3/4".
Good Luck!
Old 05-21-03, 08:35 PM
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Hello, I hope I can explain this. What you have is one supply line for hot and one for cold the second pipe is for another line that goes back into the slab and to another appliance. These are simply connections made above the slab. You should only have one connection for hot and cold at the tub valve. Work from there.
Good Luck Woodbutcher

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