Help needed with plumbing plan vent layout

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Kurt H

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Hello everyone, this is my first post. I just wanted to say I have found this sight invaluable for advice through the years, I just haven't needed to post a question before that I wasn't able to answer by searching. I am located in Canada for code reference, though I would be happy to accept advice based on the UPC if you are unfamiliar with the NPC.

The plumbing diagram below is for a mother-in-law suite attached to my house. The drain lines are how things are currently plumbed. There are currently only two areas with venting. The main floor toilet (which I'm not sure is vented ok) and most likely the three basement fixtures (which I'm fairly sure are wet vented but the drain lines are beneath the slab and I don't intend to check unless it causes me problems down the line).

This is not a pretty setup, but I want to make it function right while changing as little as possible. I have a few questions about my proposed diagram below.

1. Do you see any code violations in the drainage setup? All pipes have a proper 1/4" slope.
2. Is the venting for the main floor toilet acceptable? I have never seen one done this way before.
3. Any red flags in the rest of the venting?
4. Does anything need to be changed/added?

Thank you for your time,

Kurt

Plumbing Diagram3.jpg
 

John Gayewski

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The main floor toilet isn't right. It needs that lav to drain into it vs that wye. The other things are ok there are some efficiencies that could be made but that horizontal dry vent for the toilet is wrong just drain the lav into it.
 

Jeff H Young

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Good call on the dry vent for w/c not meeting code John. at least its easy to read the plan
 

Kurt H

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Thank you for the advice guys, I really appreciate it.

John I am not quite sure what you are saying I should do with the main floor bathroom. I understand the toilet dry vent is not right, but I'm not sure how you are saying to correct it. Could you please elaborate a little bit? Is the wye you are referring to the one that currently has the horizontal run to the main vent stack?
 

Jeff H Young

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Kurt, The main floor 3 inch vent running horizontaly is a dry vent and is prohibited from being taken horizontal lesss than 6 inches above the rim of toilet. if you could eliminate the lav line and instead use that 3 inch it would be legal
 

All Fug Duck

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If possible, put the lavatory on the 3 inch vent to prevent it from being a dry vent. also, the toilet needs to have a 1/4 bend under it to slow the momentum or it can siphon the trap when it's flushed. that's the code in my State anyway. you can skip the whole 1 1/2 line going to the lavatory that way, plus 2 inch is the minimum on it anyway.
 

Kurt H

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Thank you Jeff, I believe I understand now. The idea being to remove and cap off the current main floor sink drain/vent and instead drain/vent it directly out the main stack, creating a wet vent for the toilet? The p-trap arm from the sink will reach the vent stack in under 24", so there shouldn't be an issue. I have attached a revised plumbing diagram.

I had a few more questions.
1. There is something in the way of my planed basement wet vent going straight up to the attic. Any issue with the revised solution below?
2. A sanitary tee used for venting, like the one I circled in the attic on the diagram below, are installed upside down compared to how you would do a drain, correct?
3. What kind of fitting is appropriate for the T hub I circled in the attic. Straight tee? Sanitary tee?

Thanks again for the help!


Plumbing Diagram5.jpg
 

John Gayewski

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You can downsize that lav drain/wet vent to 2". When the other vents meet it in the attic then go up to 3".
 

Terry

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The toilet needs to have a 1/4 bend under it to slow the momentum or it can siphon the trap when it's flushed. that's the code in my State anyway. you can skip the whole 1 1/2 line going to the lavatory that way, plus 2 inch is the minimum on it anyway.
You do know that the toilet is supposed to siphon when it's flushed. It's the only fixture in the home that is "supposed" to siphon.

I think you need to buy a plumbing code book.
 

Jeff H Young

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There are several better ways but it works fine
generaly santees on all the vents those straight tees or vent tees just cost you more money and harder to find no one uses them at least Ive never seen one installed.
No Idea about reducing the 3 inch vent in your code or your minimum size through roof
 
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