3" Drainpipe Required?

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Thomas K

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I am installing stackable washer and dryer in custom built area behind wall at rear of new cast iron tub. Is it code that I have to have 3" drain for washer because it is on second floor? If so, I will have to cut out a section of 4" cast iron drain pipe below joists of second floor bathroom and install PVC 4 x 4 x 3" insert. Please respond.

Thanks!

-Thomas
 

Thomas K

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I guess I am asking if I need to have a 2" washer standpipe and P-trap connected to a 3" pipe that connects into 4" cast iron sewer line because front loading washer will be on second floor. Or is 2" drainpipe between P-trap and 4" cast iron sewer line okay?
 

Reach4

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Or is 2" drainpipe between P-trap and 4" cast iron sewer line okay?
I think yes. Under IPC, I think you would not want to have that 2 inch drain line join up with another pipe into less than 3 inch.
 

Thomas K

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I think yes. Under IPC, I think you would not want to have that 2 inch drain line join up with another pipe into less than 3 inch.

It sounds like I need to hire a plumber for install. I try to do the work I can, but I have no experience with cutting cast iron.
 

wwhitney

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I thought you were proposing to connect your laundry standpipe drain as the only fixture to an existing 4"x4"x2" cast iron fitting. Doing that with 2" plastic pipe would be fine.

Or are you proposing to first combine the laundry standpipe drain with the bathtub drain, and then take the combined drain into the 4" cast iron line?

Cheers, Wayne
 

Thomas K

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I thought you were proposing to connect your laundry standpipe drain as the only fixture to an existing 4"x4"x2" cast iron fitting. Doing that with 2" plastic pipe would be fine.

Or are you proposing to first combine the laundry standpipe drain with the bathtub drain, and then take the combined drain into the 4" cast iron line?

Cheers, Wayne
Wayne: I was going to plumb a 2" PVC DWV standpipe and trap into a 2" PVC drain line that would go down and then horizontal about 8' before dropping down and exiting block wall, terminating in a 2" fitting going into a 4" cast iron sewer pipe under house. I wish I could add pictures.
 
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Jadnashua

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If the washer is the only thing on that 2" line before it gets to the 4" pipe, I think it should be okay, but I'm not a pro! If the washer drain line were combined with something else prior to getting to that 4" line, then bumping it up would be needed. It still should get vented, though.
 

Thomas K

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If the washer is the only thing on that 2" line before it gets to the 4" pipe, I think it should be okay, but I'm not a pro! If the washer drain line were combined with something else prior to getting to that 4" line, then bumping it up would be needed. It still should get vented, though.

2" line joins 4" cast iron pipe in crawl space in same place kitchen sink drain joins. I may just cut out a section of cast iron pipe directly under where washer will be and add a 4 x 4 x 3" wye and rubber couplers . That way, pipe would drop about 2-2 1/2' from trap to empty into installed wye.
 

Thomas K

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Wayne: I was going to plumb a 2" PVC DWV standpipe and trap into a 2" PVC drain line that would go down and then horizontal about 8' before dropping down and exiting block wall, terminating in a 2" fitting going into a 4" cast iron sewer pipe under house. I wish I could add pictures.

Tub and washer drains are separate; I say second floor, but this is a split level home. I was thinking I had to have 3" drain pipe because bathroom/washer area will be on highest floor.
 

Thomas K

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I had a tech from Roto Rooter come out and check underhouse cast iron drain piping with camera and he said the pipes were good. I asked him about the washer drain and he said I could use a 2" drain pipe for second floor washer as long as nothing else connects into it. So I have one plumber saying 3" drainpipe and another saying 2".
 

Reach4

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So I have one plumber saying 3" drainpipe and another saying 2".
I am not a plumber.
See the reference to IPC 406.3 in https://terrylove.com/forums/index.php?threads/utility-tub-and-washing-machine-drain-size-requirement-of-3-ipc-406-3.63528/

The full 406.3 from the 2009 IPC is this:
406.3 Waste connection. The waste from an automatic clothes
washer shall discharge through an air break into a standpipe in
accordance with Section 802.4 or into a laundry sink. The trap
and fixture drain for an automatic clothes washer standpipe
shall be a minimum of 2 inches (51 mm) in diameter. The automatic clothes washer fixture drain shall connect to a branch
drain or drainage stack a minimum of 3 inches (76 mm) in
diameter. Automatic clothes washers that discharge by gravity
shall be permitted to drain to a waste receptor or an approved
trench drain.​

Would 2 inch all of the way work fine? Yes. But this appears to be one of the relatively few things where IPC is more strict than UPC. Often it is the other way.
 

Thomas K

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I thought you were proposing to connect your laundry standpipe drain as the only fixture to an existing 4"x4"x2" cast iron fitting. Doing that with 2" plastic pipe would be fine.

Or are you proposing to first combine the laundry standpipe drain with the bathtub drain, and then take the combined drain into the 4" cast iron line?

Cheers, Wayne
Bathtub has been relocated. Proposed line will be single 2" drain from stackpipe to 2" stub on 4" cast iron pipe. Bathtub drain now goes to another 2" pipe further down line. No other drains sharing washer drain. 1 1/2" vent will be teed near roof with one pipe going to washer trap and other going to bathtub trap.
 

Jeff H Young

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2 inch is standard here upc. but even ipc it sounds your good to go whats the problem with 2 inch ?
 

Thomas K

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IPC Inspector on DIY told me 3" drainpipe is needed for washer, but I think that he thinks I am joining a washer drain and bathtub drain on 2" drain pipe, which I was not. I also posted that I was splitting a single 1 1/2" roof vent into vent pipe for washer and vent pipe for tub.

All I can do is post a schematic on here about what I'm trying to do later on when I get home.
 
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