Looking for feedback on Drain and Vent Layout for Home Remodel

[herynkc]

I accidentally posted this in the remodel forum first. I am now reposting here since I think it is more appropriate.

The attached diagram shows the design that I am planning on going with. It is a single family home with an income apartment in the basement. Totaling 2 kitchens, 2 full bathrooms, and a laundry area.
I have a few questions and concerns before I begin:

- The relief vent for the AAV install would tee off before the AAV and then connect into the waste line downstream of where the fixtures it services are draining? This would be installed in case the drain clogged and the vent began filling up (basically a secondary emergency drain)? I have highlighted the relief vents in green.

- I have seen that you can use a 3 inch drain on an island sink and get away with not putting in an AAV or a loop vent. If I were to do this, both the waste line AND the trap would need to be 3", correct? If I am understanding this correctly, you are just making a very long trap arm and venting direct in the stack.

-Does the vent stack base have to DIRECTLY connect to the horizontal waste line as I have drawn it in my diagram? It would be great if I didn't have to run the 3 inch pipe all the way from my attic (where the branch vents tie in) down to my basement slab. My sense is that it needs to connect so the main horizontal drain has ample venting to it, however if I could get away with not running it it would save me a lot of headache. The drain would probably work pretty poorly without it?

- Can someone explain the difference between a branch vent and circuit vent. Which of the vents that I have drawn would be circuit vs branch. My understanding is that circuit vents service multiple fixtures that are not independently vented, while branch vents are vents which are dedicated to single fixtures (all of my vents would be branch?)

- I believe I've sized all the vents appropriately, however someone else may have better suggestions? We use a modified version of the 2015 UPC here in Oregon.

- When I connect my branch vents (re-vents or whatever you would like to call them) into the vent stack do I use a sanitary tee with the sweep curving upwards or downwards? Can I also use a vent tee for this application?

Thank you greatly in advance for your suggestions and information. Any feedback or comments are helpful and appreciated.

 

[James Henry]

A couple things off the bat. Go back and reread your code. Using a combination waste and vent which is what your talking about for your island sink is usually only used for floor drains. It's hard to comment on your drawing because it's not the correct way to draw a plumbing diagram. Look up plumbing isometric drawing.

 

[Sponsor]

 

[Reach4]

See wet venting diagram on https://terrylove.com/forums/index.php?threads/wet-vent-takeoff-argument.75783/#post-556664

You don't need as many vents if you use 2 inch on the lavatory, and make the toilet the last thing in line in a wet vent group.

 

[James Henry]

If that's what you like.

 

[Reach4]

If that's what you like.

He is referring to a diagram like this: https://terrylove.com/images/wet_vent_upc_3_4_bath.jpg

 

[James Henry]

I have seen that you can use a 3 inch drain on an island sink and get away with not putting in an AAV or a loop vent. If I were to do this, both the waste line AND the trap would need to be 3", correct? If I am understanding this correctly, you are just making a very long trap arm and venting direct in the stack.

If that's what you like.

 

[Storm rider]

I have seen that you can use a 3 inch drain on an island sink and get away with not putting in an AAV or a loop vent. If I were to do this, both the waste line AND the trap would need to be 3", correct? If I am understanding this correctly, you are just making a very long trap arm and venting direct in the stack.

I just replumbed a kitchen that had been done that way. That 3" pipe was about 1/3 full of 15 years of waste that hadn't washed down properly. It may be allowed by some code somewhere, but I don't think it is a best practice.

 

[herynkc]

Thanks everyone for your replies.

Wow, sounds like doing a loop vent is the better way then.

Here is another drawing that should give you more info. I hope there isn't too much information in one place.
I can also break it down into individual drawings for legibility sake.

 

[James Henry]

Put an AAV on the kitchen sink. Is your sewer 4"? I don't like 3" on that last section of drain at the wye. Just me. I've snaked to many drains. There might be other things.

 

[James Henry]

Eliminate the vent on the first floor toilet and replace the 1-1/2" lav vent with 2". The first floor shower is not clear. Looks like the vent is coming out the back.

 

[herynkc]

I appreciate your help James.

I will have to dig up that area of the slab to know if it is 3 or 4”. I will put in 4” if i can.

I think you’re referring to the bathroom in the basement not the 1st floor. So you’re saying to wet vent the toilet through the sink drain? I was planning on running a 1-1/2” drain on the lav, but in that case I would need to size it up to 2” to have enough vent for the toilet, correct? I thought it wasn’t good to wet vent toilets, though it probably wouldn’t be a problem since the toilet it the most downstream on that group. Yeah, the vent was drawn wrong on the basement shower. The drain will tee off with the vent going up.

 

[James Henry]

You have to dig up your sewer to make sure it is 4" before you consider running 4" under slab. Wet venting has become common. Terry recommends wet venting the toilet or running a vent vertically up inside a wall. He's the boss. Yes increase the lav drain to 2". you'll have to adjust your design to whatever works and passes inspection. I cant' see the little details.

 

[Plumber69]

Thanks everyone for your replies.

Wow, sounds like doing a loop vent is the better way then.

Here is another drawing that should give you more info. I hope there isn't too much information in one place.
I can also break it down into individual drawings for legibility sake.
View attachment 55482

The drawing is confusing, I see 3 vents that can easily become eliminated

 

[herynkc]

Yep it’s all 4 inch actually, based on the existing stack. Here’s a photo of it. Check out all these back to back 90s. Surprisingly there’s no issues with the toilet flushing. This whole thing is getting ripped out and redone since the bath is getting moved. If I run a 3 inch toilet drain down the wall (see yellow dotted line) can I get away with back to back long sweep 90s or am I asking for trouble? I have these bench footings all around the basement and it would be tough to do it with 45s (lots of chipping away at concrete)

 

[herynkc]

And yes, those pex lines are temporary...

 

[James Henry]

View attachment 55506 Yep it’s all 4 inch actually, based on the existing stack. Here’s a photo of it. Check out all these back to back 90s. Surprisingly there’s no issues with the toilet flushing. This whole thing is getting ripped out and redone since the bath is getting moved. If I run a 3 inch toilet drain down the wall (see yellow dotted line) can I get away with back to back long sweep 90s or am I asking for trouble? I have these bench footings all around the basement and it would be tough to do it with 45s (lots of chipping away at concrete)

Look up "stack offsets" in the drainage section of your code. Also don't use any bushings in your drainage system. Use increasers.

 

[Plumber69]

Look up "stack offsets" in the drainage section of your code. Also don't use any bushings in your drainage system. Use increasers.

Why no bush

 

[James Henry]

Some codes prohibit sharp drop offs in the drainage pipe. They specify smooth transition.