I wrote in another thread about my slow draining tub.

The consensus is that I need a vent, preferably downstream from the sink ( many mentioned an AAV just beyond the trap) now my issue is that I have a pedestal sink, and the plumbing is not really accessible around the sink to put in any kind of vent (without ripping up tile and what not).

I have easier access to the area under the tub, near the drain. My question is how would I go about installing a vent here, say just beyond the tub drain trap maybe? I know it needs to be a 45 degree bend at least off the existing drain pipe, but since it's a tight space (with the tub in the way!) can I run some horizontal vent pipe a few feet, and then go vertical to the attic and join the main stack?

Or is this a bad idea altogether?

Thanks in advance for your help.

Outofplumb

If the tub is draining slow and it has no vent then I think you will definitely be better off to install the vent closer to the tub as you are recommending. You should just need to cut a sanitary tee fitting into the drain line and then run that however you need to (horizontal/vertical, etc... ). If you want to connect the vent into other vents in the attic, that is always best, but if you want to install the AAV I would have you run it so it is above the flood level of the tub and you would be all set.

The sanitary tee fitting should roll above the center of the drain or should take off straight off the top of the drain pipe (see picture below).

I am not familiar with your last post, but have you tried to snake the drain pipe yet?

Let me know what you think...

MARK

Quote:

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Originally Posted by massplumber2008

Outofplumb

I am not familiar with your last post, but have you tried to snake the drain pipe yet?

Let me know what you think...

MARK

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Yes I did snake every inch of the pipes, and found no clogs. Thanks for the reply, that's what I wanted to hear!

There is a better picture for you. See my last post. You could also cut the vent in on the horizontal. As mentioned, you will always be better to run vent and connect to other vents, but in this case an AAV should work fine!

By the way, you don't have to run the AAV above the flood level of the tub... you only need to stub it at least 6 inches above the trap. I just like to run them up that high in case I decide to snake the tub drain in the future... this way, even if tub is full I can remove the AAV and snake drain without delays! Just FYI

MARK

Ah so the AAV only needs to be 6 inches above the trap? Even if the sink is taller?

This is good to know, one could easily hide an AAV behind a sink, out of site.

Can an AAV be mounted on a reverse L?


Something like this?
_____
_________| |
| _______| |
| | |____|
| |
| | > 6 inches above p trap
| |
| |__
|____P trap here

Opps that graphic didn't work too well...

Hi Doza:

YUP! Even if the sink is taller!

Here, the mechanism that allows air to enter the system is a spring loaded flapper that drops when waste passes by it causing the flapper to drop and allow air into the system. If say, the sink was clogged the waste would not go by the spring mechanism fast enough to open it and air would not be allowed into the system. In fact, the water would have a tendency to push against the spring loaded mechanism and help to close the AAV so no water can escape! Hope that made sense.

You would have to explain the REVERSE L better for me to answer the last question... ;)

MARK

Picture an AAV on the same picture above that goes up 6 inches and is mounted horizontally off that 6 inches. So a reverse L shape.

My sink drains into what I believe is the vent stack. My tub however drains into the house main drain and that connection is located 10 feet lower than the vent stack. Do I need a separate vent for my tub?