Tying new sink drain into tub drain?


Old 01-14-15, 04:58 PM
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Tying new sink drain into tub drain?

Hello everyone. First post on here, hoping you plumbers or experienced diy'ers could help me.

I have been brain storming a possible relocation of our kitchen sink. Its a project that would be way down the line, if ever.

Is it possible to tie the new sink drain into an existing bathtub drain? In the new, potential sink location, its a straight-forward run in the floor joist cavity to the tub drain. To route it back to the existing drain would involve a bit more. The tie-in would be after the trap of the tub. Also, the drain pipe from the tub is galvanized pipe (grayish color?). I presume it wouldn't be a problem fitting a T into it, with those gasket-type sleeves, and pvc from the new sink drain. I don't believe there would be any problem with slope, as the tub drain runs under the floor joists (in the basement) and the sink drain would be within the cavity.

As for venting, I don't know how that works. I suppose one of those air-admittance valves?

Again, just thinking out loud.
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Old 01-15-15, 06:10 AM
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As long as the plumbing codes are followed there is no restriction as to what fixtures can go on what line. When you think about it they all end up tied together into one line eventually.

Also read up on venting. Generally an air admittance valve is only permitted in certain circumstances like a sink in an island where it's impossible to run a vent line up. They are not permitted so you can be lazy and avoid running a proper vent in a wall.

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