I'm in the process of remodelling my third floor and adding a new bathroom up there. The previous owners put in a new 4" vent stack which is currently only connected to a washer on the second floor. They had intended on putting a bathroom in themselves on the third floor but never did, and they did not bother to run the vent stack through the roof. Instead, the stack sticks up out of the floor about 5ft, and there is some kind of filter on the top of it.

The problem is, I would like to put the bathroom on the opposite side of the room, approx 16 feet away and vent it out through the roof there. I have a straight shot under the floorboards to do this.

So, essentially, I'm asking whether it is ok to run a vent stack straight up from the basement to a third floor, then run it horizontal for 16 ft (making sure it drops 1/4" per foot), and then 90 degree verticle again and through the roof.

Any assistance on answering this question would be appreciated.

Thanks in advance

Hi Rgb71...

YUP! No problem on using the 90s, however, plumbing codes would recommend long sweep 90s, OK? Be sure to maintain that 1/4" pitch so you have no issues in the future.

Also, note here that the washing machine will need to have an 1.5" vent installed and connected to other vents upstairs at 42-48" minimum of the floor.

If codes allow, you might also install a mechanical vent (called an AAV), but most cities/towns won't allow them. No matter what, you need to add the vent to the washing machine or the PTRAP will get siphoned out as the large volume of water from upstairs rushes by to the basement sewer and sewer gasses will escape from the washer drain... ;)

More questions? Let me know...

Mark

Hi Mark,

Thanks for the quick response. Much appreciated!

Glad to help. Pop back if you need any help on the venting, OK?

Mark