Author Topic: Steps to add toilet under stairs? USA  (Read 548 times)

mozar

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Steps to add toilet under stairs? USA
« on: July 11, 2019, 03:31:35 PM »
Hello, my goal is to have a competant conversation with the plumber. I want to add a sink and toilet to my downstairs closet under the stairs. I think I can remove the plaster under the stairs to make the required clearance of 7ft. And there is 30 inches by 20 inches clearance for the toilet. The existing toilet upstairs would be on the same wall as the downstairs toilet. Would that help lower the costs? Could the new downstairs toilet be connected to the existing waste line?
The closet is also next to the kitchen. Could the new sink be connected to the existing sink plumbing? I'm also open to Google-fu suggestions as almost all advice I've seen is from the uk.

Papa bear

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Re: Steps to add toilet under stairs? USA
« Reply #1 on: July 13, 2019, 05:25:12 AM »
What’s below the room? Is it basement? Is it accessible?

The biggest issue with adding a bathroom to a space that doesn’t have one deals with the waste plumbing. The toilet requires a 3” waste line and the sink requires 1 1/2” pipe. The toilet is where you run into issues.  Getting that 3” line to run somewhere without removing structure can be difficult.  Hopefully you get lucky, but that’s the big issue.  I have never met a plumber that would do a proper job of running a 3” line through structure.  They all hack it apart and compromise the home.  I’m in the middle of 2 bathroom rehabs that had this exact problem. 

If you’re lucky, the waste runs will be easy and accessible. If you have basement below and you are ok with pipe below the floor joists, that makes it easy too. 

Beyond the waste line, you need to make sure the bathroom is vented properly, which may require installation of vent pipe above your bathroom.  Then you have supply lines for the sink and toilet.  Those shouldn’t be an issue as they are typically 1/2”.

Figure on a plumber being pretty expensive for this.  4 figures plus wouldn’t not be unheard of.


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mozar

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Re: Steps to add toilet under stairs? USA
« Reply #2 on: July 13, 2019, 10:43:01 AM »
I do have a crawlspace. I would have to get they key from the HOA. I was quoted 6k to put the toilet in the laundry room. So 4 digits is OK. Is it possible to find and expose the waste line from the upstairs plumber myself so the plumber doesn't have to hack anything? Or will they have to build a new one anyway?

bacchi

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Re: Steps to add toilet under stairs? USA
« Reply #3 on: July 13, 2019, 11:57:04 AM »
Whether you can use the same waste line depends on the current pipe diameter and your local code. 2 toilets often require a 4" pipe.

mozar

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Re: Steps to add toilet under stairs? USA
« Reply #4 on: July 13, 2019, 12:28:54 PM »
I see. Do you think I should talk to an inspector first before I talk to a plumber?

seattlecyclone

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Re: Steps to add toilet under stairs? USA
« Reply #5 on: July 13, 2019, 05:47:42 PM »
Are you aware of sinks like this one that fit on top of a toilet tank to save space and water all at the same time? My friends have one like this. It allowed them to fit a half bathroom in a space that would not have had room for a sink that was separate from the toilet. The sink starts up when you flush, drains into the toilet tank, and runs until the tank is full. Then the used sink water flushes the toilet next time.

Papa bear

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Re: Steps to add toilet under stairs? USA
« Reply #6 on: July 13, 2019, 06:33:10 PM »
You’re not going to know what you’re getting into, how to plumb it, or how much it’s going to cost until you open up some walls, unfortunately.

It’s going to be impossible for us here in online world to give you straight answers.  Even someone on site might not be able to figure it out until everything is open.


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mozar

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Re: Steps to add toilet under stairs? USA
« Reply #7 on: July 14, 2019, 12:15:07 PM »
I would rather have a separate sink if possible.  And those tiny sinks are so adorable.
I did open up the wall under the stairs to see what the clearance is. I can open up the back wall too. I don't want someone to come in and start hacking with a hammer. The advice to open up the wall is helpful.