Vanity Waste line

[Vincent McMahon]

Good evening,

I am installing a vanity in our master and have the following Waste line rough-in. I am curious as to what is the second outlet for (above and to the left of main waste water line). Its currently capped off flush with the sheetrock.

See attached image

Any idea's?

thanks

 

[John Gayewski]

Some kind of vent afterthought it looks to me.

 

[Sponsor]

 

[Terry]

The tee downstream would need an AAV in the cabinet for venting the p-trap.

 

[Vincent McMahon]

Thanks, @John Gayewski

Is a vent needed for this vanity? The whole waste line system is vented in numerous locations, and the line that this waste line is coming off of is vented next door. Can I safely cover this over or do I need to figure out a vent?

 

[Vincent McMahon]

@Terry

hi Terry, I had just replied to John when I saw your response. Does each vanity need its own, or given the main line is vented next door would this be sufficient?

Can I safely put a studoor in under the vanity

 

[Reach4]

Can I safely cover this over or do I need to figure out a vent?

You need to vent before the line turns down, and before the path of the 1-1/2 inch pipe gets to 6 ft.

That vent afterthought is not good in that a vent line is required to stay within 45 degrees of plumb until it is over 6 inches above the sink. I am not saying that if you used a 90 to go vertical on that horizontal fitting and lead to an AAV under the sink would not work. But the path was not supposed to go horizontal.

So you can cut out that sanitary tee that is glued in now, and put one in tilted up at 45. Then use another 45 to turn the path vertical, and put the AAV above that. Bottom of the AAV needs to be more than 4 inches higher than the horizontal pipe (which is called a trap arm until it is vented).

The AAV needs to be accessible for replacement.

 

[Vincent McMahon]

Thank you @Terry @Reach4

I will install a vent as described. Is there ever a risk of grey water backing up and out of this vent, since it will be lower than the sink.

 

[Terry]

I will install a vent as described. Is there ever a risk of grey water backing up and out of this vent, since it will be lower than the sink.

Unless your line a clogged, backing up into the AAV is not a worry. Four inches or higher above the trap arm helps with that.

 

[Vincent McMahon]

I ended up cutting out the 90 coming out of the wall on the right side and capping it off at the Tee. As it turns out it was 1 inch too low for the vanity we purchased (Its an open bottom vanity so the pipe work has to be above the false bottom)

I will use the outlet on the left side as the waste line and install the AAV on that inside of the vanity.

thanks for your help guys

 

[Reach4]

I will install a vent as described. Is there ever a risk of grey water backing up and out of this vent, since it will be lower than the sink.

The AAV is a one-way valve. But if that failed and you had a clog in the drain line, it is possible to get water coming out of there. I don't know how likely such a failure is. It can't be that likely. Probably more probable than getting hit by a meteorite or a person who buys 100 powerball lottery tickets per year winning the big jackpot.