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Old 03-08-2009, 06:41 PM   #1
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Help with putting in an attic bathroom...PLEASE! :)

Hey guys,

The pics are of what I am proposing to be done, in order to tie into the existing plumbing.

Is it possible to create an additional stack, parallel to the existing vent/waste stack, and tie into the basement? Then, in the attic, vent the new waste pipes above 6 inches?
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Old 03-08-2009, 07:03 PM   #2
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I can't read the second drawing.

But t looks as you adding a bath to the main floor not the attic.

Code does not allow for the vent to terminate in the attic..must terminate out roof or where impossible use a properly sized AAV

What size is the vent stack?

What all is alredy connected to the waste/soil stack? Need to figure dfu


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Old 03-10-2009, 04:44 AM   #3
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We want to add a second bathroom in the attic, which we are finishing.
We want to splice into the waste stack in the basement with a second waste stack which would run up to the attic.
In the attic, the newer wast stack would have a toilet, sink, and shower tied into it. Then, we would tie back into the vent in the attic, so that the second stack would be vented out the roof.
In the basement, the wast stack is at least 5 inches, I think. The only wast tied into the basement is the 1st floor shower, toilet, and sink.
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Old 03-10-2009, 06:08 AM   #4
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It is possible to install a bathroom above the level of existing fixtures and vent it via an connection to an existing vent stack through the roof, but if I'm reading your diagrams correctly not in the way in which are proposing to do it.

There are number of code requirements that govern how this can be done, for starters the fixtures in the bathroom will have to be vented from above, as in this example,

rather than a few inches off the floor at the junction with the stack as shown in your diagram.

Laying out the DWV than plumbing for a new bathroom in an existing structure in a code compliant manner can get quite complicated, your design will be subject to approval by your local building department and the various details of the actual installation will be subject to inspection, you may find it simpler to have this portion of your project performed by a plumber even if local regulations allow you to do it yourself.


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Last edited by Michael Thomas; 03-11-2009 at 09:29 PM.
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Old 03-11-2009, 07:21 PM   #5
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Ok, so in order to put in a second bath, we have to update all plumbing in the entire house?
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Old 03-11-2009, 09:51 PM   #6
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No, you dont have to update all the plumbing in the entire house. Yes you can tie into the stack in the basement and run a new waste stack to the second floor as long as the existing stack is large enough for the additional fixtures. From what you've described it sounds like you've got a 4" stack existing which should serve the additional DFU load just fine. Run your drains in the attic off the new waste stack, vent your fixtures, tie your vents together and run them either out the roof on their own or tie into an existing vent in the attic. Just be sure everything is properly sized. Check with your plumbing inspector to be sure you follow your local codes.
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Old 03-12-2009, 04:38 AM   #7
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Ok, thank you. This makes much more sense to me. If we do not do it on our own, how much do you think would be a fair price to rough in the plumbing upstairs? We can then tie in on our own.


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