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Rick
Rick, Construction Supervisor
Category: Plumbing
Satisfied Customers: 13687
Experience:  Licensed Master plumber with 40+ yrs. experience.
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Question about vent sizes and drain configuration

Resolved Question:

I recently purchased a home and decided to tear our the existing bathroom. So far I've tore out the entire bathroom to the studs and capped the existing supply lines. I'm confident in my skills to re-run the supply and drain lines; however, I have a question regarding the drains and vents.

The old bathroom was rather crazy in its plumbing design - the toilet used a 4" cast iron stack for drainage and venting, the sink used a 2" ABS line for drainage and the 4" cast iron stack for venting, and the tub used the 2" ABS line for drainage and a 2" steel pipe for venting. Crazy, I know. Also, the old tub had drainage problems with no blockage in the drain line - my guess is that the vent is clogged or blocked somehow.

In the new bathroom, I will be pulling out the old cast iron stack from the roof flashing all the way to the drain into the floor and will be pulling out the 2" steel pipe that was previously used for venting. And here are where my first question comes in - what size vent pipe should I use in this application? For this vent, there will be all of the fixtures in the bathroom (one sink, one toilet, one whirlpool tub), plus the utility sink in the basement. The total feet from the utility sink to the roof flashing is roughly 25 feet, and from the bathroom to the roof flashing is roughly 20 feet. From reviewing the plumbing code handbook my state uses, it appears that a 2" vent pipe will sufficiently vent all of these fixtures, so I want to be sure that you'd recommend this as well.

And for my second question - after removing the existing cast iron stack, I will be replacing it with a 4" ABS pipe into the concrete floor. The utility sink in the basement has its own main drain; however, I am wondering what is the best way to tie in all three drains? All three of the drains will be along a single wall that is 8 ft long and are in line with each other (closest to the door, sink->toilet->tub). The critical distance between any of these drains and the vent pipe would be under 8 ft. What design would you recommend for the ABS drains? The sink drain will be 2", toilet drain 4", whirlpool tub 2" (although I am debating making it 3").

Thank you in advance for your advice.
Submitted: 4 years ago.
Category: Plumbing
Expert:  Rick replied 4 years ago.
HiCustomerbr />
Assuming the bathroom is the highest interval (nothing above it) you can stack vent toilet and lavatorary (drain connected directly to stack at same level as the fixture trap). The tub can also be stack vented if the drain comes off the stack at the same level as the toilet and is within 6' of the stack. If the tub is further than 6' to the trap or does not tie into the stack at the same level you will need to run an 1 1/2" back vent taken off the horizontal at least 45 degrees above the mid-line and tying back into the stack above flood level of the highest fixture. Your utility sink will also need an 1 1/2" back vent also tying into the stack above the highest fixture. If you take the lav drain off the horizontal it will need to be vented in a similar manner (1 1/2" vent).

Your bathroom sink only needs an 1 1/2" drain, 2" for the tub is larger than necessary (1 1/2" is all that is required) 3" is serious overkill. Your toilet can be either 3" or 4".
Customer: replied 4 years ago.
I think I understand what you're saying, but perhaps you could offer a little bit of clarification?

Here is an image I found online regarding the drainage configuration -
http://www.renovation-headquarters.com/images5/bathroom%20drain%20plumbing%20cr.jpg

The above image is fairly close to what I will be doing. The lavatory is a little over 6' away from the vent, so I can tie it in using 1 1/2" vent and connect to the stack above the flood level of the highest fixture. The tub is right next to the vent, so I can simply tie the drain into the stack vent and that should work properly. Same for the toilet.

Based on the picture, and my further clarification, is this correct?
Customer: replied 4 years ago.
I re-wrote the question to clear up any confusion - please review, and re-respond. Thank you much.

================================================================

I'll give some background information and then ask my questions:

I recently purchased a home and decided to tear our the existing bathroom. So far I've tore out the entire bathroom to the studs and capped the existing supply lines. I'm confident in my skills to re-run the supply and drain lines.

The old bathroom was rather crazy in its plumbing design - the toilet used a 4" cast iron stack for drainage and venting, the sink used a 2" ABS line for drainage and the 4" cast iron stack for venting, and the tub used the 2" ABS line for drainage and a 2" steel pipe for venting. Crazy, I know. Also, the old tub had drainage problems with no blockage in the drain line - my guess is that the vent is clogged or blocked somehow.

In the new bathroom, I will be pulling out the old cast iron stack from the roof flashing all the way to the drain into the floor and will be pulling out the 2" steel pipe that was previously used for venting.

The plumbing, both supply and DWV, will be completely new.

My questions are regarding the drains and vents. First, what size vent pipe should I use in this application? For this vent, there will be all of the fixtures in the bathroom (lavatory, toilet, whirlpool tub), plus the utility sink in the basement. The total feet from the utility sink to the roof flashing is roughly 25 feet, and from the bathroom to the roof flashing is roughly 20 feet. From reviewing the plumbing code handbook my state uses, it appears that a 2" vent pipe will sufficiently vent all of these fixtures, so I want to be sure that you'd recommend this as well.

After removing the existing cast iron stack, I will be replacing it with a 4" ABS pipe into the concrete floor. The utility sink in the basement has its own main drain; however, I am wondering what is the best way to tie in all three drains from the bathroom? All three of the drains will be along a single wall that is 8 ft long and are in line with each other (closest to the door, sink->toilet->tub). The critical distance between any of these drains and the vent pipe would be under 8 ft. The sink drain will be 1 1/2", toilet drain 4", whirlpool tub 2".

The new stack will be at 4" at the base level and taper to 2" above the last drain into the vent stack.

I had originally planned to install a closet bend for the toilet and connect to the 4" soil stack, critical distance being >6', so I was not going to install an additional vent for this and rely solely on the vent stack.

The tub will have a 2" P-trap, and will be vented up through the wall and connect to the vent stack.

The sink will have a 1 1/2" P-trap, and will also be vented up through the wall and connect to the vent stack.

Also, I will be roughing in for a new bathroom on the second story of the house. This bathroom will be vented up through the attic and will connect to the vent stack near the roof flashing.

In conclusion - I am pulling out the existing 2" vent and the 4" cast iron vent stack. In its place, I will be putting a 4" ABS pipe into the floor and running all DWV pipes off of that.

My questions are these:

1.) Am I approaching venting these pipes properly? Properly, in this case, being installing a back vent taken off the horizontal at least 45 degrees above the mid-line and tying back into the stack above flood level of the highest fixture for both the first story lavatory and tub, along with the second story lavatory and toilet. The first story toilet will vent directly into the vent stack since it is <6' from closet bend to waste T.

2.) What is the best way to tie all of the waste pipes together? I know that this is a loaded question, but a little bit of advice in this area should go a long way. My question here revolves mainly around fittings and couplings.

Thanks again for your advice.
Expert:  Rick replied 4 years ago.
Any fixture's vent in the first floor bath including the toilet must tie into a separate (minimum) 2" vent stack which ties back into the main stack above the highest fixture. On the top interval (floor) the toilet can be stack vented and the tub can be stack vented if the drain comes off the stack at the same height as the toilet. If you use a Y off the stack for the tub you will need to back vent that as well. To take the tub off at the same level we use an estabrook (a sanitary T with a side outlet).
I'm not sure what you mean by the "best way to tie all the waste pipes together". All I can offer is that any branch drain should connect to the main with a Y except for branches directly off the stack which can be TY's (sanitary T). All 90 degree turns should use long radius fittings (or 2 45's together) except when the flow is from horizontal to vertical (not vertical to horizontal). You need a clean out at the base of the stack.
Customer: replied 4 years ago.
Remaining questions:

"Any fixture's vent in the first floor bath including the toilet must tie into a separate (minimum) 2" vent stack which ties back into the main stack above the highest fixture" - is this based on highest fixture per interval, or for the stack?

Toilet can be stack vented, check.

So for my bathroom, I will stack vent the toilet using a TY, and the lavatory will connect to the main with a Y, creating a branch drain.

As for the tub, I will connect it into the side outlet of the estabrook, correct? And the toilet will connect as usual into the sanitary T.

As for fittings on the stack, should the Y for the branch drain be above or below the estabrook, or does it really not matter?
Expert:  Rick replied 4 years ago.
An interval is a floor level. First floor all fixtures must be individually vented into a minimum 2" vent stack (toilet vent must be 2" everything else 1 1/2"). Only the toilet on the top floor can be stack vented. The second floor toilet and tub tie into an estabrook cut into the stack. The Y for the lav can be above or below since you are venting it individually.
Rick, Construction Supervisor
Category: Plumbing
Satisfied Customers: 13687
Experience: Licensed Master plumber with 40+ yrs. experience.
Rick and other Plumbing Specialists are ready to help you
Customer: replied 4 years ago.
Rick, one more question and I'll throw a bonus at you -

For the first floor lavatory - am I able to tie the individual vent into the vent stack below other fixtures and not have any problems? It would be fairly difficult to have the individual vent tie into the vent stack above the other fixtures that are on the floor above me, so I am wondering what my risk is.

Thanks!
Expert:  Rick replied 4 years ago.
You can tie all the fixture vents on the first floor together (above the flood level of the highest fixture on the first floor) into the 2" vent stack then connect the 2" vent stack to the main stack above the highest fixture.
Customer: replied 4 years ago.
Is this true even though I will have fixtures on the floor above which will also be tying into the vent stack from their branch vent?
Expert:  Rick replied 4 years ago.
You tie the 2" vent stack into the main stack separately. This is what the code allows.
Customer: replied 4 years ago.
I understand - perhaps I'm not being clear, I apologize for that. For the first floor lav vent, do I need to connect the vent above the fixtures from the second floor bathroom, or can I connect the vent to the stack vent below those second floor fixtures?
Expert:  Rick replied 4 years ago.
You need a SEPARATE vent stack for the first floor. All the first floor fixture vents connect to this separate vent stack. This separate vent stack connects to the main stack above the highest fixture in the house. You tie your individual first floor fixture vents into the separate vent stack above the highest fixture on the first floor.
Customer: replied 4 years ago.
Fantastic. Thanks for your patience and answering all of my questions.
Expert:  Rick replied 4 years ago.
Thanks for using Just Answer

A Bonus would be appreciated

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