Bathroom Remodel - Cast Iron Repipe and Removing Galvanized Drains

[Mandelbaum]

Good afternoon all!

I have been lurking for a while while I peruse the 2021 IPC codes required by the State of Virginia, and I think I'm ready to consult the knowledge on this forum for some guidance or thrown spears (either are welcome) about my plan to repipe a couple of bathrooms.

I'm currently amidst a remodel of my master bathroom for a home built mid-1960s. Most pipes are either cast iron or galvanized and thus I'd like to future-proof myself against corrosion issues as I continue to remodel this home from the top down. Essentially, I intend to replace everything with modern materials while I have good access and open walls.

Below is a sketch of the current bathroom configuration on the second floor. The right bathroom, or BR#1, is my current project. Here are some consolidated details. Keep in mind the drawings are not to exact scale but should paint the picture.

1) The 3" soil pipe runs up through the roof as the main sewer vent and currently catches both water closets from BR #1 and #2. I do not know if they are back to back, or staggered. It is hub cast iron, and in my mind, needs replacement.

2) The lavatory catches the tub drain from the adjacent bathroom and has a galvanized individual vent through the roof, as well as a galvanized drain pipe down. I believe this drain runs into the concrete slab foundation and into the main sewer drain.

3) The shower currently runs into a galvanized drain down into the foundation, and also has its own individual vent.

Here is my proposed changes. Directly below BR#1 is a mechanical closet containing the air conditioning unit, the furnace, and my electrical panel. It is out of sight. I'd like to:

1) Replace 3" hub cast iron soil stack with 3" PVC.

2) Run the shower, lavatory, and BR#2 tub into the mechanical closet under all floor joists so I don't have to make any holes or notches, combine them, and run them into the 3" soil pipe rather than their own galvanized drains.

3) Run both bathroom water closets in 3" PVC to the soil stack, likely underneath the lavatory, tub, and shower tie-ins to avoid any issues with siphoning.

4) I will maintain the individual vents to the shower and lavatory/tub, except I will tie them into the 3" soil/waste stack vent in the attic instead of having them all individually terminate through the roof, which seems unnecessary.

Here is a side view of the soil stack detail. Essentially, plan is to combine all drains in PVC into the soil stack to minimize the number of individual drain lines that run into the slab to prevent future issues.

Here are my specific questions:

1) Am I overthinking this, and should I simplify the renovation by utilizing the galvanized drain pipes that are already in place, and simply make repairs in the future if I need to? Or continue with my plan to consolidate all drains into a new 3" PVC soil stack?

2) For assumed back-to-back water closets, it seems like I should utilize a double fixture fitting. But if I have the room, should I simply stagger the attachments of each WC to the soil stack (denoted with "option 2" in my last sketch above? I think I should have the room to stagger them.

3) Any violations with tying the individual vents into the 3" stack vent in the attic? Seems like it should meet IPC, just making sure.

4) Any reason I wouldn't want visible PVC in my mechanical closet? Seems like it's the easiest way to go without cutting wall studs and floor joists at the expense of them being visible, but I think I could eventually box them in. It's also a mechanical closet and I don't care how it looks, if anything it's easier access for clogs and I could potentially add a cleanout as well.

I'm sure I missed some details. I did not include all necessary fixtures, bends, etc. in my sketch but I think I can get smart with the 2021 IPC to make sure I don't do anything too crazy.

Thank you all!

Jake

 

[Mandelbaum]

Going to answer my own question here with a little more reading.

Water closets utilizing the soil stack vent as a vertical wet vent will have to connect at the same elevation based on IPC. Or I could dry vent one of the toilets if I intended to use two stacked san-tees, but then I would have to figure out how to run that vent in the space I have.

I'll take a look at the space again, but my way forward now likely will be both water closets connecting back-to-back with a 3x3x3x3 double wye with street 45s, and then running a 2" common vented tub/lav into the 2" individually vented shower and then connecting both into the stack below the water closets with a 3x3x2" san-tee.

 

[Sponsor]

 

[Jeff H Young]

not quite catching how the shower and tub are venting but otherwise seems like solid plan

 

[Mandelbaum]

not quite catching how the shower and tub are venting but otherwise seems like solid plan

My scribbles are pretty unclear, but master shower has its own vent currently that I’ll tie in to the vent stack in the attic.

Second bathroom tub and master bathroom lavatory share a common vent where they intersect.

Is there any reason why the bathroom fixtures can’t connect past the two water closets into the soil stack? Seems like it’s poor form to connect a wet vented fixture after the toilet, but for two individually vented fixtures, I think that should be good to go.

 

[Reach4]

1) Am I overthinking this, and should I simplify the renovation by utilizing the galvanized drain pipes that are already in place, and simply make repairs in the future if I need to? Or continue with my plan to consolidate all drains into a new 3" PVC soil stack?

I think the wet vents from lavs to toilets are suppose to be 2 inc or bigger. Your 1.5 inch galvanized might work, but not to code. I think you could keep the 1.5 galvanized venting the lavatory santee, but the path below the santee I think should be 2 inch.

2) For assumed back-to-back water closets, it seems like I should utilize a double fixture fitting. But if I have the room, should I simply stagger the attachments of each WC to the soil stack (denoted with "option 2" in my last sketch above? I think I should have the room to stagger them.

Double wye or staggered wyes would be better.

4) Any reason I wouldn't want visible PVC in my mechanical closet? Seems like it's the easiest way to go without cutting wall studs and floor joists at the expense of them being visible, but I think I could eventually box them in. It's also a mechanical closet and I don't care how it looks, if anything it's easier access for clogs and I could potentially add a cleanout as well.

I see no problem with that. Note that PVC is available as dual-rated solid as well as DWV-only foamcore. Solid may be quieter, but I am not sure of that. Solid is stronger, but you don't need extra strength.

Riser clamps can help support your vertical runs.

 

[John Gayewski]

Replace any galvanized drain. Vents are ok galvanized, but there's no real reason to leave them as plastic won't rot amd metal will eventually.

Plan seems mostly good. Maybe just keep posting with some pictures down the radios as your building it.

 

[Mandelbaum]

I appreciate you all for the responses. I think to remove the galvanized drains, the easiest solution will be removing a section of the soil stack as planned and tying in with new PVC to allow all bathroom fixtures to drain into the stack in 2”. There is an old furnace chimney that is no longer used so I plan to use that space in the wall to drop my common vented tub and lav into the mechanical closet to be tied into the stack at some point.

Progress photos to come as I build it, right now I’m still removing plaster and rock lathe walls and replacing a rotten subfloor.