Plumbing in concrete slab - new construction

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  #1  
Old 12-05-02, 08:13 AM
Diego
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Question Plumbing in concrete slab - new construction

I am building a small guesthouse. It will be a slab on grade. Before I have the slab poured, I need to set in place any plumbing that will penetrate the slab. I have read many posts here, but still don't quite understand the "rules".

What do I put in place for the toilet and shower before the pouring is done? How do I protect those items to be sure they are not filled with concrete?

Thanks for any help. I'm a real amatuer.
 

Last edited by Diego; 12-05-02 at 08:38 AM.
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  #2  
Old 12-05-02, 08:44 AM
Join Date: Dec 1999
Location: Northeastern NC On The Albemarle Sound
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Cool

The first thing that you need to do is to check with your Building Inspection Department for all local codes.
You need a Building Permit and inspections anyway.
You will need to layout and stub-out (well above the pour level) all of the plumbing that is to be in the slab. The drain lines will need to be sloped 1/4" per linear foot, and there will need to be traps under tub/showers, and vents tied back into the main stack. Toilets have built in traps.
You need to get a book on Plumbing, I think, if you've never down any.
Good luck!
Mike
 
  #3  
Old 12-05-02, 09:22 AM
Diego
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Thanks so much for the reply. This construction is out in the country where there are no permits or code enforcement (except septic). I bought a couple of plumbing books and they are very helpful, but they never seem to talk about slab construction (which is common here in Texas).

The things I can't seem to find out are:
Do the waste pipes that go through the slab sit tight in the concrete or do you have to put something around them during the pour so they can still move around?
Also, the flange that holds the toilet in place. Is it in place during the pour? Do I somehow have to make room for it so that the top surface of the flange will be even with the floor?

I appreciate all help!

Thanks.
 
  #4  
Old 12-05-02, 09:42 AM
Join Date: Dec 1999
Location: Northeastern NC On The Albemarle Sound
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Diego,
(I'm originally from East Texas---Gladewater).
Anyway, if I were you, I would use either black plastic ABS or white plastic PVC for drain lines, and go with plastic CPVC for hot and cold water supply lines.
Here is an illustrated article on CPVC plumbing from Reader's Digest "The Family Handyman" magazine that should help you: http://www.familyhandyman.com/200007/cpvc/main.html
Here is an another article on plumbing a half-bath that should help, too: http://www.familyhandyman.com/200002/project/main.html
You can pour directly on the lines, as long as the drains maintain the proper slope.
They are all just hacksaw and glue (or primer and glue) work.
If you went with copper water lines, the concrete might corrode the metal, plus you would have to do a lot of soldering.
The only traps that would be below the pour would be for shower/tub unit and washing machine drain. Vents are tied into the main vent after traps. Toilets have built-in traps, and sink drains have the traps under the sink.
Stub-out the closet bend drain pipe for the toilet. The flange is glued into it after you complete the finish flooring level. Then you drill, anchor and bolt the flange to the top of the finish floor level, and then bolt the toilet to the flange. Only the thickness of the flange itself should be above finished floor level.
 
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Old 12-05-02, 02:53 PM
Diego
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Galdewater! Well, not too far from me. I'm just north of Mineola near a town named Golden.

Your comments are just what I needed. Thanks very much for hte help.
 
  #6  
Old 12-05-02, 08:20 PM
Join Date: May 2001
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Also put what is called closet rap around the closet bend stub so the concrete does not go against it. This will make it easier when you go to put the flange on. It also may help to do the same on the shower so the pipe is not so ridgid. Duck tape works well to keep things (concrete) out of the pipes. Make sure each fixture has its own vent and size it all correctly.

Good Luck
 
  #7  
Old 12-05-02, 10:11 PM
Diego
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John,

Thank you so much. Will a place like Home Depot know the term closet wrap? Is it a thin foam material?

Thanks.
 
  #8  
Old 12-06-02, 01:39 PM
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Dont worry so much about the closet rap, just turn up 4" pipe for the water closet instead of 3" so that the flange will glue INSIDE the pipe instead of OVER the pipe, that way the concrete wont interfere... this is now a code connection where it used to be outlawed... it happens to be the best connection that could be made too...
 
  #9  
Old 12-06-02, 01:57 PM
Diego
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Will do. Thanks.
 
  #10  
Old 12-07-02, 05:07 AM
cool_filup
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in my area of MO the plumbers run flexible copper with no solders under the slab into a central location st the water heater then out to all the sinks and toilets with more flexible copper. these are placed in the gravel base and wrapped with tar tape where they come through the slab. the toilet drains are stubbed up above the concrete level and formed around so that area is not poured so it can have some adjustment after the wall is in place. then on finish a bag of ready mix is mixed and poured in around the stool flange. I hope I didn't confuse things.
 
  #11  
Old 12-07-02, 05:23 AM
Diego
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Sounds like another good technique. Thanks for the information.
 
  #12  
Old 12-07-02, 11:33 AM
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609.3 Water piping installed within a building and in or under a concrete floor slab resting on the ground shall be installed in accordance with the following requirements:

609.3.1

Ferrous piping shall have a protective coating of an approved type, machine applied and conforming to recognized standards. Field wrapping shall provide equivalent protection and shall be restricted to those short sections and fittings necessarily stripped for threading. Zinc coating (galvanizing) shall not be deemed
adequate protection for piping or fittings. Approved non-ferrous piping shall not be required to be wrapped.

609.3.2

Copper tubing shall be installed without joints where possible. Where joints are permitted, they shall be brazed and fittings shall be wrought copper.

Note: For the purpose of this section, “within the building” shall mean within the fixed limits of the building foundation.

313.0

Protection of Piping, Materials, and Structures

313.1

All piping passing under or through walls shall be protected from breakage. All piping passing through or under cinders or other corrosive materials shall be protected from external corrosion
in an approved manner. Approved provisions shall be made for expansion of hot water piping. Voids around piping passing through concrete floors on the ground shall be appropriately sealed.

END CODE

People you need to read the code.
 
  #13  
Old 12-07-02, 12:16 PM
Diego
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That helps. Thanks.
 
  #14  
Old 12-07-02, 01:48 PM
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Actually I didnt see where anyone suggested anything against code Plumber2000? He said to run water piping under the concrete with as few joints as possible and to wrap it where it came in contact with the concrete with tar tape (an approved method if the inspector says so since that is one use of the tape)... so where was anyone missing on code?
 
  #15  
Old 12-07-02, 04:33 PM
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Hey Ron, WELCOME BACK!

Third post , Diego said no permits, code, or enforcement....Run bamboo, more flex than copper....
 
  #16  
Old 12-07-02, 10:07 PM
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Actually if you wanna really save some cash you can whittle your hotwater tank out of an old oak stump too... Lefty has one like that in his basement...
 
  #17  
Old 12-16-02, 02:42 AM
Houllx
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I am building a home in Texas right now. In the city and our code calls for a thick coating of pitch to allow for expansion to protect the PvC that penetrates the slab. PITCH "typical tar used for roofing" Just coat all PVC that will have concrete around it, including drain lines that cross through load beams in the concrete. This is supposed to keep your PVC from breaking when your slab expands and contracts from temp and humidity. That is what I was told anyways. Good luck
 
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Old 12-16-02, 05:39 AM
Diego
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Great, Thanks.
 
  #19  
Old 12-16-02, 07:51 AM
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Since freezing doesn't seem to be a problem there, why not run all the water pipes through the attic instead of the slab? Less headaches, and easier to repair if something does go wrong.
 
  #20  
Old 12-19-02, 08:37 PM
Diego
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Well, we have occassional freezing. Also, I would still have to deal with the toilet and shower drain.

Thanks.
 
  #21  
Old 12-23-02, 06:23 PM
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Lightbulb Check new contruction

Check out some new construction sites in your area to see how they do it.
This will give you a visual on how it is done
Personally I like to oversize the supply pipes (use 1" PVC for the cold lines, 3/4" cpvc for the hot) this way you will never have to worry about someone flushing while you are in the shower !!!
 
  #22  
Old 12-23-02, 06:29 PM
Diego
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Great. Thanks!
 
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