Main stack is rotting away and leaking.


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Old 02-01-21, 08:19 PM
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Main stack is rotting away and leaking.

As the title says, my 3" main stack is made of 60 year old copper and is leaking due to rot. I need to replace the entire section which unfortunately connects to my kitchen sink and first floor toilet.
While it would be easy for me to simply replace what is there, I'd like to do it to code.

The toilet is drained with a 90 degree elbow, which then connects to the main stack via sanitary tee. The entire run from toilet to stack is about 2 feet. In between is a 1.5" vent tee which runs horizontally for a foot and then vertically.

1. Is there a need to install a clean-out in lieu of the 90 elbow?

2. Given the short run from toilet to main stack, is a vent even needed?

3. If a vent is needed, should I reorient the 1.5" vent tee so that the tee faces vertical rather than horizontal? The final result would be something like this (without the trap).


The kitchen sink is connected with 1.5" ABS. The entire run is about 5 feet and connects to the main stack via Wye tee. It is not connected to a vent.

4. Do I need to connect this run to a vent?

5. Can I swap the Wye tee for a sanitary tee?
 
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Old 02-02-21, 05:08 AM
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1. No, the toilet counts as a cleanout since it can be removed if needed.

2. You said there was a vent connection in that 2' long run, so I would leave it. It may or may not be required depending on how many fixtures are connected to your vent stack. Are you sure it's a vent? Where does the bathroom sink drain?

3. Do you even have the space to have the vent enter the horizontal run on the top side? Usually that is not an option.

4. Code allows a vent to be up to 6' away from the trap of a 1 1/2" line. Since you are close to the limit I would add a vent close to the trap end if possible, especially if you've noticed odd draining issues with the sink.

5. There are rules as to where a wye and sanitary tee can be used. Often they are NOT interchangeable.
 
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Old 02-02-21, 09:51 AM
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Are you sure it's a vent? Where does the bathroom sink drain?
Pretty sure it's a vent. The pipe goes in the opposite direction of where the bathroom sink is.
Don't hold me to this but the only other thing it could be is either the drain or the vent for the second floor shower. I remodeled the second floor bathroom and the shower vent pipe was of similar type/size/location as the pipe in the basement. I have no clue where the shower drain resides.

3. Do you even have the space to have the vent enter the horizontal run on the top side? Usually that is not an option.
It's an unfinished basement, the toilet is incredibly close to the main stack and everything is located next to the foundation. I am going to have to replace the toilet flange anyways so I could lower the pipe 6 inches for clearance. Isn't a horizontal tee configuration more prone to clogging from toilet water backing up into the vent pipe?

 
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Old 02-02-21, 10:14 AM
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No need for a vent on your toilet drain at its length. 3" pipe can run 6' without a vent, so you're good there. But I do find it odd to have one there... could be the shower drain maybe? Would be an odd configuration.

I would upsize your kitchen drain to 2" and forego the vent. Some codes are starting to require a 2" drain for the kitchen sink. Plus, it gets you further without requiring a vent. I'd definitely ensure you have a 1/4" slope on that drain and that it's set at an appropriate height for the sink.

But just to confirm with your sink drain, it goes into the wall and runs horizontally to the stack, it doesn't drop below the floor first, right? Because if it drops down, then you'll need a vent.

going horizontal to vertical on a drain you can use a San Tee or Combo Wye. So into your main stack, it doesn't matter, pick the appropriate one based on the space you have available.
Vertical to vertical (parallel pipes) makes sense to use a wye. And if you're going horiz - horiz or vertical to horizontal, a wye is required.
 
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Old 02-02-21, 11:49 AM
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could be the shower drain maybe? Would be an odd configuration.
Yeah, I'm struggling with this as well. It's either a vent, a shower drain or a vent for the shower. It is connected to the toilet line via sanitary which leads me to believe it's a vent. Wouldn't a drain in horizontal orientation be connected via Wye?

But just to confirm with your sink drain, it goes into the wall and runs horizontally to the stack, it doesn't drop below the floor first, right? Because if it drops down, then you'll need a vent.
It goes into the wall, down to the basement and then horizontal to the stack. It currently doesn't contain a vent (and I'm pretty sure a licensed plumber installed it). Although, I am currently not experiencing any drainage issues.
 
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Old 02-03-21, 06:28 PM
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It goes into the wall, down to the basement and then horizontal to the stack.
Based on UPC/IPC, that configuration would need a vent up and out the roof, or an AAV. Since it drops down, you immediately need a vent.

Some local codes don't require vents for kitchen sinks in that configuration, which is one reason some codes are updating the kitchen sink to a 2" drain.
 
 

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