Adding a bathroom on second floor


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Old 04-01-10, 09:53 PM
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Adding a bathroom on second floor

Hi, I am adding a bathroom on the second floor of my cape.

The house has a center stairway and the upstairs has two rooms. In the middle of these two rooms I am going to add a dutch dormer (about 5x7) for the bathroom.

Here is my problem.

The stack vent is positioned in my wet wall downstairs and as it goes upstairs, it is in the center of the upstairs hallway. I hoped to use the wet wall as the place to run my drain for my upstairs toilet.

I dont think the toilet should be in the middle of the room. I also dont want to shift my upstairs bathroom three or four feet in either direction because I would be taking space away from each room unevenly.

I guess the main question is, must the toilet drain go straight down, or I run it through a coupel of joists to get it in the bay that I want?

Thanks.
 
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Old 04-02-10, 06:34 AM
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No it does not need to go straight down however it does need to vent so you need to keep it close to the stack or run another vent. The distance you can run from a vent depends on the size of the pipe that you are using.
 
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Old 04-02-10, 09:20 AM
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thanks so much.

But is there more of a chance of clogging if the toilet waste pipe runs horizontal in a bay (or through joists) for , lets say two feet, before going down though?

Also, I would be going through two joists. They are 2x8s and I figure the waste line wil be a 3 or 4 inch... Is that going to weaken the joists? Teh hole would be drilled towards the back of the joist where it is sitting on top of the plate - not in the center where it is weakest anyway.
 
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Old 04-02-10, 11:36 AM
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The waste line running horizontal (actually slightly downhill) won't be proned to clogging. At some point, every drain and waste line in the house runs horizontally, and how often do they clog?
 
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Old 04-02-10, 01:12 PM
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I guess I was thinking that, if it starts out horizontal (slight slope), that there would be slow drainage at the very beginning, and that, for a sink, it wouldnt matter because it is all water which flows unimpeded.

But, for example (not to get graphic) lets say there is a lot of "waste" from the toilet. Well, it isnt all water. I would think it would make a big difference if you first went straight down for about two feet. This would hold the volume from an entire flush, so the speed of drainage would be meaningless if it slowed up after making a horiontal turn.

But if, from the start it is horiontal and drains a bit slower - it could back up.

Am I simply not understanding the physics of plumbing?
 
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Old 04-02-10, 03:01 PM
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Smile

You are overthinking your drainage, if you have proper fall on the horizontal line it will drain fine.
 
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Old 04-02-10, 04:11 PM
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Like I said, every drain that exists in the house right now, including the toilets, has some horizontal waste line in it, and probably a lot more than the 2' or so that you are thinking about for this one.

Since they aren't a problem, this one won't be either, as long as you give it 1/4" per ft. slope.
 
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Old 04-02-10, 05:19 PM
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Great - thats great news.

Last question then, do I need a 4 inch pipe for toilet waste?

Thats what my main bathroom has but I have heard 3 inch is ok.

Would it matter for drainage?
 
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Old 04-03-10, 06:34 AM
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Three inch is fine for the toilet
 
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Old 11-07-10, 05:32 PM
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question

I'm buying my first home. Our house-to-be is a similar type of cape, and we are wondering approximately how much such a dormer would cost. We'd be taking the closet at the top of the stairs and adding at least a standing shower (if no room for a tub) and a toilet. The seller says that the piping is already set up for a bathroom.



Thanks in advance!
 
 

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