Water closet stack vent IPC code clarify

[Keepyoucool2003]

Hello all,
I am remodeling our master bath and ran into an issue relocating our water closet 1’. I’ve consulted the IPC and find myself confused on horizontal offset stipulations based on existing findings.

2 story house, 3” waste stack running vertical from the basement.

It comes up, 45s x2 to get into wall cavity, pickups up a kitchen sink branch tied in horizontally. Sink has its own dry vent terminating to the stack above the highest flood rim.

The stack then travels vertically, offsets 45deg to get out of wall framing, and then immediately has a double 3” street wye and 45 out the top center to continue vertically to pickup shower via San t 3x3x2, vents tie in and out to roof.

The picture is looking at the right side of the wye, the white bag is stuffed where I cut the old shower out between the two pics.


Can I tie the water closet located 18” left of the stack into the stack without a Separate dry vent? Or are the 45s considered offsets requiring separate dry vents?

They had a shower was tied in at the 3x3x2 San t on the stack with no vent, it was 36” from the tie in. The existing street t for shower without any vent is making me question if that was appropriate. Production build of the 80s, they build a soffit and put nothing in it below.


There isn’t a lot of room as usual so I’m looking to purpose the old water closet dry vent for my shower vent.

Thank you.

 

[MicEd69]

They had a shower was tied in at the 3x3x2 San t on the stack with no vent, it was 36” from the tie in.

There are no fixtures draining into the 3" stack above that old shower 3x3x2 San T, correct? If so, the shower was dry vented by that 3" stack. And replacing that 3x3x2 San T with a 3x3x3 San T will be just fine for your toilet.

 

[Keepyoucool2003]

There are no fixtures draining into the 3" stack above that old shower 3x3x2 San T, correct? If so, the shower was dry vented by that 3" stack. And replacing that 3x3x2 San T with a 3x3x3 San T will be just fine for your toilet.

Correct. edited to clarify.

 

[MicEd69]

You are good to go then. Dry vent lines must be vertical, or no more than 45 degrees off vertical, until they reach 6" above the flood plan of the fixture being served. After that, they can be "horizontal" with a 1/4" per foot slope back to the vent stack. So, the 45s above the connection of the toilet are considered vertical per the code, but if they are 6" above the toilet bowl, then they could even be "horizontal".

 

[Keepyoucool2003]

You are good to go then. Dry vent lines must be vertical, or no more than 45 degrees off vertical, until they reach 6" above the flood plan of the fixture being served. After that, they can be "horizontal" with a 1/4" per foot slope back to the vent stack. So, the 45s above the connection of the toilet are considered vertical per the code, but if they are 6" above the toilet bowl, then they could even be "horizontal".

Okay complicating this more. The existing vent after it comes off rolled SanT with 45, has has a section of horizontal pipe to get though a floor joist before they 90 to vertical. Is that to code?

Is there anything wrong with the sketched arrangement?

 

[MicEd69]

In my first answer, I was just concentrating on the question about the feasibility of changing the 3x3x2 SanT to a 3x3x3 SanT for the toilet.

The SanT on its back rolled at a 45 that you label as the Old WC Vent in your first picture was a code problem to begin with. The only way that would be allowed by IPC would for that to be a wet vent and the fitting would have to be a wye or combo. And there are many plumbers and inspectors that do not allow a SanT on its back for a vent connection like that even if it didn't have a horizontal piece before it is 6" above the flood rim of the fixture being served.

Your sketch does have the same code issue. In your sketch, the shower MIGHT be wet vented by the drain line to the left of the 2x2x2 wye where it enters the horizontal drain. It appears as you are attempting to vent the shower, and the toilet as well, with the 2x2x1 1/2 SanT on its back rolled 45 degrees like the original installation. As that line goes horizontal before it goes above the flood rim of the shower, that is not allowed. But I thought you were going to put the toilet in place of the old shower SanT like below.



I don't know where your shower drain goes in your new layout. You may be able to replace that 90 on the horizontal 3" where it goes down into a wye you said with a 3x3x3 SanT and tie it back in to the 3" vent stack above. That is assuming the 3x3x2 is being replaced with a 3x3x3 SanT for the toilet and it is rotated towards the toilet location to allow clearance.

 

[user 32496]

Hello all,
I am remodeling our master bath and ran into an issue relocating our water closet 1’. I’ve consulted the IPC and find myself confused on horizontal offset stipulations based on existing findings.

There isn’t a lot of room as usual so I’m looking to purpose the old water closet dry vent for my shower vent.

The answer to the first question is, "No". the existing toilet dry vent is not a legal vent. It goes horizontal (greater than 45 degree bend) prior to being above the flood plain. Luckily, that vent isn't needed for your existing toilet configuration (because distance from toilet to vent is not specified in IPC) but it won't work to vent the new shower (because it goes horizontal prior to being above the flood plain).

Okay complicating this more. The existing vent after it comes off rolled SanT with 45, has has a section of horizontal pipe to get though a floor joist before they 90 to vertical. Is that to code?

No

Is there anything wrong with the sketched arrangement?

It's hard to figure what's exactly going on in the sketch but two rules to remember:
1) your trap weir must not be below the weir of the trap.

IPC (2006) Section 906.2
906.2 Venting of fixture drains. The total fall in a fixture drain due to pipe slope shall not exceed the diameter of the fixture drain, nor shall the vent connection to a fixture drain, except for water closets, be below the weir of the trap.

UPC 905.5 The vent pipe opening from a soil or waste pipe, except for water closets and similar fixtures, shall not be below the weir of the trap.

This basic scientific statement always trumps the simple length taken from a table and is the real key to preventing a situation where a siphon could form.

the trap has to see the vent.


If the vent opening is below the trap weir, a siphon can be created.


Illegal vent situations:



2) Secondly; a vent can not go horizontal prior to being above the flood plain. Horizontal is more than 45 degrees. A less than 45 degree bend is considered vertical for a vent and is allowable.

 

[Keepyoucool2003]

In my first answer, I was just concentrating on the question about the feasibility of changing the 3x3x2 SanT to a 3x3x3 SanT for the toilet.

The SanT on its back rolled at a 45 that you label as the Old WC Vent in your first picture was a code problem to begin with. The only way that would be allowed by IPC would for that to be a wet vent and the fitting would have to be a wye or combo. And there are many plumbers and inspectors that do not allow a SanT on its back for a vent connection like that even if it didn't have a horizontal piece before it is 6" above the flood rim of the fixture being served.

Your sketch does have the same code issue. In your sketch, the shower MIGHT be wet vented by the drain line to the left of the 2x2x2 wye where it enters the horizontal drain. It appears as you are attempting to vent the shower, and the toilet as well, with the 2x2x1 1/2 SanT on its back rolled 45 degrees like the original installation. As that line goes horizontal before it goes above the flood rim of the shower, that is not allowed. But I thought you were going to put the toilet in place of the old shower SanT like below.

View attachment 42525

I don't know where your shower drain goes in your new layout. You may be able to replace that 90 on the horizontal 3" where it goes down into a wye you said with a 3x3x3 SanT and tie it back in to the 3" vent stack above. That is assuming the 3x3x2 is being replaced with a 3x3x3 SanT for the toilet and it is rotated towards the toilet location to allow clearance.

These may help.


This is a headache trying to work in things already wrong for 30 years in 2x4 framing. They built a bulkhead below this originally and put nothing in it, seems this should have been done differently
I have room to do just about anything using that.


If I’m following what is allowed from the responses.

Replace the stack San T with 3x3x3 San steet T serving the WC, not needing a separate dry vent.

new 2” shower drain will head towards the left wall, install a wye directly under that wall to get my vertical vent, come out of the wye with a 90 to drop vertically into the bulkhead,then long sweep 90 to head back toward the stack branch, install 2x2x1.5 wye to pickup existing 1.5 Lav branch, continue 2” to the existing 3” branch. Does it matter bushing vs reducer on horizontal run?

I’m an hvac & electrical guy, going the opposite direction didn’t occur to me before.

Tie the 1.5” shower vent into the 1.5” dual Lav vent in the attic.

 

[Keepyoucool2003]

In my first answer, I was just concentrating on the question about the feasibility of changing the 3x3x2 SanT to a 3x3x3 SanT for the toilet.

The SanT on its back rolled at a 45 that you label as the Old WC Vent in your first picture was a code problem to begin with. The only way that would be allowed by IPC would for that to be a wet vent and the fitting would have to be a wye or combo. And there are many plumbers and inspectors that do not allow a SanT on its back for a vent connection like that even if it didn't have a horizontal piece before it is 6" above the flood rim of the fixture being served.

Your sketch does have the same code issue. In your sketch, the shower MIGHT be wet vented by the drain line to the left of the 2x2x2 wye where it enters the horizontal drain. It appears as you are attempting to vent the shower, and the toilet as well, with the 2x2x1 1/2 SanT on its back rolled 45 degrees like the original installation. As that line goes horizontal before it goes above the flood rim of the shower, that is not allowed. But I thought you were going to put the toilet in place of the old shower SanT like below.

View attachment 42525

I don't know where your shower drain goes in your new layout. You may be able to replace that 90 on the horizontal 3" where it goes down into a wye you said with a 3x3x3 SanT and tie it back in to the 3" vent stack above. That is assuming the 3x3x2 is being replaced with a 3x3x3 SanT for the toilet and it is rotated towards the toilet location to allow clearance.

Hopefully the below clears it up. The elevation wouldn’t work. I was forgetting they made San Street Tees, not stocked locally in ABS here.