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Add vents to these vanities?

401 Views 4 Replies 3 Participants Last post by  Dan1973
I'm embarking on a total re-do of my bathroom. House built in 1961 and all fixtures and plumbing are original.

The waste drains are all galvanized steel which I will change to PVC. I am also moving them slightly to accommodate the new vanity. As I suspected, they are not vented individually, but rely on the vent in the wall behind the toilet, which ties in to the cast iron stack in the basement. The sinks are 36" part, and the closest sink is about 30" from the vent. New position will be about 4-6" closer to the vent, so when done a total of 5' (give or take) from the existing vent.

Should I open up more of the wall and tie them into the vent behind the toilet? They drain fine as is, but since everything is opened up I don't mind going the extra mile here. I know the vents will need to be at least 6" higher than the vanity's overflow, and should slope back toward the drain slightly to allow condensation or rain to drain away.

Current galvanized pipe is 1.5". Vents should also be 1.5 until it meets the existing vent, correct? (Toilet vent is 3" I believe.)


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Not trying to eliminate anything - there is only 1 vent pipe that services the toilet, 2 sinks and the bathtub on the other side of the room. Everything flows from right to left in the photo with the toilet being the hight point of the cast iron waste stack in the basement. The only vent is positioned right behind the toilet.

Motivation is to make sure I'm doing it correctly and according to modern standards as much as possible. I've got the walls open so now's the time!
That's what I thought - thanks for confirming. Nothing drains from above.
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