I was a little confused about wet and dry venting in your last response, but I am still confused. So I am going to backtrack to try to get on the same page with you.OK, if you can vent the sink to the roof instead of using an AAV, which appears easy to do as the proposed vent to the roof looks pretty close to the sink, then the toilet will be wet vented through the sink drain line and the dry vent for that sink. If you use an AAV for the sink, then that will not adequately vent the toilet, only the sink. Assuming you can do that, then the "new vent" needs to be disconnected from the 3" sewer line and only connected to the shower drain line before it connects to the 3" main. Then that vent can run following the same path as it is now, then up, and then connect to the sink vent at an elevation of at least 6" above the top of the sink. This is what I would do as it provide a good vent and I dislike mechanical devices for vents. They must be accessible, and they will fail in time.
Now theoretically, if you disconnect the vent line from the 3" main and connect it to the drain line from the shower before it hits the 3" main, I think the toilet will be properly wet vented through the short section of the shower drain between the vent and the 3" line, and then by the dry vent for the shower up to the roof. That way, you could use an AAV for the sink, if you wanted to.
But by venting the sink to the roof and combining the shower vent to the vent stack from the sink at least 6" above the top of the sink, you would provide dual paths for air to properly vent the toilet.
"I think your response was based on the purple shaded region (the dry vent going to the shower, and then connecting right after the toilet and then going to the wall and finally to the roof). Are you saying if I do that, then all 3 parts of the bathroom would be vented properly and an AAV is not necessary?"I was a little confused about wet and dry venting in your last response, but I am still confused. So I am going to backtrack to try to get on the same page with you.
I think your response was based on the purple shaded region (the dry vent going to the shower, and then connecting right after the toilet and then going to the wall and finally to the roof). Are you saying if I do that, then all 3 parts of the bathroom would be vented properly and an AAV is not necessary?
If so, where I am getting confused is when you said, "OK, if you can vent the sink to the roof instead of using an AAV, which appears easy to do as the proposed vent to the roof looks pretty close to the sink, then the toilet will be wet vented through the sink drain line and the dry vent for that sink."
Wouldn't the sink and the toilet be wet vented since the dry vent is not at or above the flood rim level.
"1. Water closets and bathtubs or shower stalls in bathroom groups may be wet vented by the lavatories. (this seems to be what we are doing)"On another note I was looking at this:
12.10.3 Bathroom Groups
- Water closets and bathtubs or shower stalls in bathroom groups may be wet vented by the lavatories. (this seems to be what we are doing)
- The dry vent pipe from the lavatories shall be not less than one-half the size of the drain pipe for the group.
- The size of wet vent piping shall comply with the following: (1) be not less than one pipe size larger than the required drain pipe size for its upstream fixtures, and (2) be not less than one pipe size larger than one-half the size of the largest connected drain piping being wet vented downstream.
- The connection of fixture drains to horizontal wet vents shall be horizontal. Except for water closets, the upper portion of the wet vent opening shall not be below the weir of the fixture trap. (Does this mean that the vent line that connects to the shower arm should not be above the centerline?)
- The bathtubs or shower stalls may be connected to their water closet drain upstream from its wet vent connection. (We are in violation of this with the current setup right?)
- The maximum length of the fixture trap arms for lavatories, bathtubs, and shower stalls shall comply with Section 12.8.1.
- The maximum length of the water closet trap arms to their wet vent connection shall comply with Section 12.8.4, horizontally and vertically.
- Where fixtures are wet vented vertically, water closets shall connect to the wet vent at the same lowest elevation. Bathtubs or shower stalls shall connect to the wet vent at the same elevation as the water closets or higher.
Best bet is a proper horizontal wet vent, running 3 inches. And 2 inches from the most upstream that becomes the wet vent......I just did a bathroom for my nephew in his basement. I dumped the toilet first, then shower, I dropped a dry vent with cleanout in between shower and vanity into the 4" main. I stubbed the vanity up 3" with a cleanout on the backside and then 2" up to sink and AAV off the top. All vents were accessible AAV's. The inspector was fine with it because all my fixtures were within limits from a vented line. I did not put individual vents to any of the fixtures and the vanity was the only wet vent. I think your best bet is to run that piping then call for inspection and see what he tells you. I did have to install a backwater valve as they are code in his city and I forgot to have him ask when he applied for the permit.
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