Re: Venting lavatory sinks
Posted by e-plumber on March 20, 2004 at 13:32:05:
In response to Re: Venting lavatory sinks
: I am remodelling my bathroom and the position of the vanity basins is to be moved. I thought I could just drain the new basins into the same drain that the shower and bath go into but looking around your site it seems that this is more complex. I had never heard of venting until I checked out your site! Can someone advise me on how I should do this?

: The bathroom is on the top floor. At present the bath tub drain runs about 10' sloped horizontally, the shower drain runs about 5' - they both are 1 1/2" ABS pipes which join in a Y into a 2" drain which has a 2" vent pipe to the roof which eventually T's into a 3" pipe out through the roof (many other 2" and 3" pipes T into this as well). The existing vanity basins have their own vent pipe but I can't get to this because of the joists.

: On the same wall that the new basins are to be installed there is another 3" vent pipe but I am not sure what it is venting as there is no bathroom beneath this.

: So my questions:
: 1. Is it ok to run the new vanities into the same drain as the bath and shower?
: 2. Do I need a new vent?
: 3. Can I T into another vent pipe or do I have to run a new pipe to the attic and T into the 3"? Cutting the holes for a new pipe will be very difficult so I would like to avoid this.
: 4. If I have to run a new vent should it be 2"?

: Hope you can help,
: Phil

Reply:
Does the existing bathtub and shower drain traps each have their own individual vent lines connected next to their traps?

1. Is it ok to run the new vanities into the same drain as the bath and shower?
>The existing 2" should handle it with no trouble, tie into a horizontal drain with a wye.
2. Do I need a new vent?
>Yes, all fixtures need to be vented, if you're installing double lavs on the same counter, you can connect them with one trap and one vent, (within 30", C to C)
3. Can I T into another vent pipe or do I have to run a new pipe to the attic and T into the 3"? Cutting the holes for a new pipe will be very difficult so I would like to avoid this.
>Either way, you probably will not overload an existing vent line.
4. If I have to run a new vent should it be 2"?
>The double lavs require an 1-1/2" vent.

Good Luck. e-plumber



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