Bathroom Drain/Vent Design

[jmterail]

I am designing a new bathroom + kitchen sink on a second story. Will need to tie everything into the 4" stack.

Could you take a look and let me know if my idea makes sense? There a section of "wet" vent, where I have a kitchen sink draining above where the toilet discharges. Is that okay?

Second question is cleanouts - code says to the include one at every change in direction. What does that mean? Does that mean I need one where every fixture discharges into the 3" branch? this is a second story... all is going to be covered by flooring ... so I don't know how I'd keep them accessible.

I did include a cleanout at the end of the horizontal branch...which is basically the only spot that will be accessible. Is there anywhere else I need cleanouts?

Tried to use wyes, tees, and bends in all the right places...but I'd appreciate your input.

Thanks so much!

 

[Shoestring]

What does the 4” stack serve now? If it is a vent from the first floor then this is a no go, if it’s not a vent, The only thing I see is your branch serving the washer and lavatory is over sized. 2” will pick this up. The cleanout is not necessary above the first floor according to UPC, the waste stack can be 3” instead of 4”, and the vent through the roof can be 2” as long as all of your vents in your home add up to 12.5 square inches or more. Wet vented section needs to be 3”

 

[jmterail]

What does the 4” stack serve now? If it is a vent from the first floor then this is a no go

I was worried this might be an issue.

Here's the story.

This is a 100+ y/o duplex, with kitchen and bathroom on both levels. Most of the drains have been upgraded from cast iron to pvc by previous owner. None of it was vented properly - it all drains direct to the main stack (which I assume was how it was originally done with the cast?).

Apparently, despite that, it all worked without issue.

I have gutted the upper unit, including all previous drains, and intend to do the upper unit properly (have a permit). Everything thing in the upper unit previously drained into this stack, so I figure I am not making anything "worse." (and in fact, I'll be improving things, because at least the upper level fixtures will be properly vented).

Despite the fact that there is no proper venting for the main unity fixtures, however, I guess the stack is perhaps still acting as a makeshift wet vent for those main level fixtures - and I am technically making it "wetter" by draining upper unit fixtures into it.

I only see three options:

1) Do as I propose, and hope that the "I'm not making it worse" argument will fly with an inspector (think this is likely?), knowing that the drainage did work previously without lower fixtures properly vented.

2) Do a second stack from the upper unit that terminates below the lowest fixture on the main stack - that way I am not interfering with any of the existing "venting" provided to those lower fixtures by the main stack.

3) try to run a second vent from the lower unit fixtures, to above the highest fixture in the upper unit - that way the lower fixtures are properly vented regardless of whether I am adding drainage to the main stack .

Options 2 and 3, if I am being honest, are logistical nightmares given the lower unit is occupied. Any tips? Is there an option I am not thinking of?

 

[jmterail]

The only thing I see is your branch serving the washer and lavatory is over sized. 2” will pick this up.

Assuming I can fix the larger issue above...

I thought I needed a 3" branch because bathroom + clothes washer = 9 DFU (per: https://www.engineeringtoolbox.com/drainage-fixture-unit-values-d_1077.html)

And I thought the max DFU for a 2" horizontal branch was 6 DFU (per: https://www.engineeringtoolbox.com/drainage-fixture-units-piping-load-d_1078.html)

Although that seems to suggest I could get away with 2.5".

Thanks for your help.

 

[Shoestring]

I was worried this might be an issue.

Here's the story.

This is a 100+ y/o duplex, with kitchen and bathroom on both levels. Most of the drains have been upgraded from cast iron to pvc by previous owner. None of it was vented properly - it all drains direct to the main stack (which I assume was how it was originally done with the cast?).

Apparently, despite that, it all worked without issue.

I have gutted the upper unit, including all previous drains, and intend to do the upper unit properly (have a permit). Everything thing in the upper unit previously drained into this stack, so I figure I am not making anything "worse." (and in fact, I'll be improving things, because at least the upper level fixtures will be properly vented).

Despite the fact that there is no proper venting for the main unity fixtures, however, I guess the stack is perhaps still acting as a makeshift wet vent for those main level fixtures - and I am technically making it "wetter" by draining upper unit fixtures into it.

I only see three options:

1) Do as I propose, and hope that the "I'm not making it worse" argument will fly with an inspector (think this is likely?), knowing that the drainage did work previously without lower fixtures properly vented.

2) Do a second stack from the upper unit that terminates below the lowest fixture on the main stack - that way I am not interfering with any of the existing "venting" provided to those lower fixtures by the main stack.

3) try to run a second vent from the lower unit fixtures, to above the highest fixture in the upper unit - that way the lower fixtures are properly vented regardless of whether I am adding drainage to the main stack .

Options 2 and 3, if I am being honest, are logistical nightmares given the lower unit is occupied. Any tips? Is there an option I am not thinking of?

Choice 2 is the proper one.

 

[Shoestring]

Assuming I can fix the larger issue above...

I thought I needed a 3" branch because bathroom + clothes washer = 9 DFU (per: https://www.engineeringtoolbox.com/drainage-fixture-unit-values-d_1077.html)

And I thought the max DFU for a 2" horizontal branch was 6 DFU (per: https://www.engineeringtoolbox.com/drainage-fixture-units-piping-load-d_1078.html)

Although that seems to suggest I could get away with 2.5".

Thanks for your help.

Not knowing which code your jurisdiction uses, the UPC assigns a clothes washer 3 DFU and a lavatory 1 DFU with 2” horizontal pipe maximum of 8 DFU.

 

[jmterail]

Choice 2 is the proper one

Thanks for your helpful replies.

Wouldn't option 3 technically be the best? Not only would I not be interfering with lower fixture venting - but I would actually be properly venting them, which they are not now (ie I would essentially be creating a bypass vent around the section of the main stack into which the upper fixtures would drain - with a separate vent from each lower fixture joining above the fixture rims and up to the attic).

Ultimately I'd like to go with whichever option is logistically most feasible (which I haven't determined yet).

 

[Shoestring]

Thanks for your helpful replies.

Wouldn't option 3 technically be the best? Not only would I not be interfering with lower fixture venting - but I would actually be properly venting them, which they are not now (ie I would essentially be creating a bypass vent around the section of the main stack into which the upper fixtures would drain - with a separate vent from each lower fixture joining above the fixture rims and up to the attic).

Ultimately I'd like to go with whichever option is logistically most feasible (which I haven't determined yet).

I suppose it could be, I (possibly incorrectly) was envisioning your 4” stack as a stack vent with wet vented fixtures on the first floor.

 

[jmterail]

I suppose it could be, I (possibly incorrectly) was envisioning your 4” stack as a stack vent with wet vented fixtures on the first floor.

I don't think you are wrong.

But if I dry vent each main floor fixture up through the walls, reconnecting with the stack in the attic, haven't I essentially turned that main stack vent into a soil stack, that can be used as a waste drain for the upper unit?

I only ask because it might be that running (1.5"?) dry vents through the walls from each of the main floor fixtures is easier than trying to get a new 3" waste stack down to the basement drain.

 

[Shoestring]

I don't think you are wrong.

But if I dry vent each main floor fixture up through the walls, reconnecting with the stack in the attic, haven't I essentially turned that main stack vent into a soil stack, that can be used as a waste drain for the upper unit?

I only ask because it might be that running (1.5"?) dry vents through the walls from each of the main floor fixtures is easier than trying to get a new 3" waste stack down to the basement drain.

Yes. If you remove all venting requirements from the 4” stack, it should suffice as a waste stack with the exception of San tees. If your waste stack on the first floor is wet venting fixtures and you cut in vents on the trap arm to remove the venting requirements from the stack, the San tee that you leave behind now should be a wye branch fitting. 1-1/2” pipe will vent just about everything (8 DFU @ 60’) in your home except the toilet, that needs to be 2”.

 

[Diehard]

When comparing one fixtures flow to pipe capacity you should look at GPM directly.
FU's are meant to be added up and incorporate a diversity factor, for when more than one fixture may be in use.
(based on the rate of discharge, time of operation and frequency of use of a fixture.)