Toilet (Closet) flange and drain pipe sizing and type.

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Leif

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I am building a house where the living area is on a second story level over a garage. There are two bathrooms and they are both upstairs. The living area floor is precast concrete and I am getting ready to do my plumbing rough in. The underground plumbing is a 4" PVC pipe that presently comes out of the garage slab and sticks up a few feet. I am wondering what size toilet drain pipe and size of the other drains for showers and sinks. I need to rent a core drill and bits. I don't know if you drill an exact size opening in the concrete or if you oversize it a bit. Any advice is greatly appreciated.
 

Sylvan

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I always use 4" but your local code may allow 3" for the toilet and other fixtures
 

Terry

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You will want to oversize the holes some. Have some pipe on hand so that you will know the sizing you will need.
Where I'm at we run up to three toilets on 3" and on the 4th bump up to 4". Sewer lines outside the home have been 4" here.
 

Jeff H Young

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You will want to oversize the holes some. Have some pipe on hand so that you will know the sizing you will need.
Where I'm at we run up to three toilets on 3" and on the 4th bump up to 4". Sewer lines outside the home have been 4" here.
Same here I have heard of inspectors allowing a 4th w/c addition without requiring increasing pipe size. a well installed system with proper grade etc aint going to notice a toilet added
 

Leif

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Do I gain anything by stepping down to 3". It appears the Oatey flange is for 3 or 4 inch and goes inside or outside the drain pipe depending on the pipe size. I think that would mean I still need a core drill big enough for the toilet flange as the determining factor. Do any of you have advice on what toilet flange part number to use?
 

Master Plumber Mark

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Do I gain anything by stepping down to 3". It appears the Oatey flange is for 3 or 4 inch and goes inside or outside the drain pipe depending on the pipe size. I think that would mean I still need a core drill big enough for the toilet flange as the determining factor. Do any of you have advice on what toilet flange part number to use?


Yes, you will gain a whole lot of elbow room to work with if you step it down to three because working with 4 inch pvc in -between rafters can be very challenging , tight and really not worth it if you are only installing 2 toilets anyway..... reduce it down to 3 inch and it can do everything just fine for even up to a 3 bathroom situation.... In our state you can do up to 4 toilets on a vertical 3 inch pipe.... .it will work fine as long as you have good enough fall.....
 

Jeff H Young

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Im with Master Mark on this easier to work wit 3 inch and it performs fine . Is bigger better probebly but in 99 percent of cases youll never know . So if its easy enough go ahead and run 4 . I wouldnt but your the boss !
 
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