Whole House Drain Line Replacement

[Nathan-KC]

So I am working through replacing all of the cast iron and galvanized steel drain and vent piping in a home I just purchased. The cast is cracking and the galvanized is rusting and joints are falling apart. I won't even get started on the clogged supply lines, that is the next project.

I have removed the cast and the galvanized and have started replacing with PVC. I have applied for a permit and so want the work to be up to code for inspection and peace of mind reasons. The home is in Kansas City, MO, and from the City's website, it appears that they have adopted the UPC 2012 regulations for their code.

I have attached a diagram of the general plan for the system. (Pitch is not indicated but will slope at 1/4 inch per foot)

I think I have most things figured out (fingers crossed), but have 4 main questions that I hope someone can help with.

1. The 4 inch cast soil stack utilized a San T on its back to tie the 2nd floor WC to the stack. The WC is within 6 feet of the stack so the stack should act as the toilet vent? Since the stack at this point is only a vent, and the space in the wall is tight, my hope is to replace with a San T again instead of trying to fit a Wye into the space?

2. In the basement, what types of T fittings should I use for the connections of the drains into the soil stack? I assume the 1st floor WC needs a San T because it is getting its vent from the 2 inch vent connection into the top of the Wye section of the stack. As far as the other T connections, does it matter Wye vs San T? I assume it really doesn't matter because all of the lines, apart from the 1st floor WC, are vented before they hit the stack?

3. What should I do about the hack job of notches in the floor joists of the 2nd floor bathroom. I have reworked the drains so that I don't need to utilize any of the notches or holes from the previous install. Do I cover them up, sister small spans with plywood, or not worry about it since the house is over 50 years old, and they haven't caused a problem yet?

4. While I have the walls open, my plan is to run a 2 inch "Future Vent" for the addition of a basement bathroom in the future. You can see the vent in the diagram. My thought is to tie it into the bottom of the stack as shown. When time to add basement bathroom, cut vent above basement fixture flood level and then run venting to fixtures. Remove lower San T, break up concrete floor and tie basement bathroom into 4 inch line running under basement slab. Is this the correct way to plan for this possible future addition?

Help is greatly appreciated.

Thanks

 

[Standardairconditioner]

Without a scaled blueprint or 3D view of the home, it is difficult to approve any designs at best.

It looks to me there are too many unnecessary vents. Most, if not all, can be drained directly the main stack.

For instance, I have no idea why you have the 2nd floor WC/Tub/Lav all on seperate drains, same with the 1st floor Lav/WC/Laundry. If I didn't know any better, it appears you are trying to give each device its own drain, which is completely unnecessary in a residential home.

Since this is a major project, it is strongly suggested that you get a local professional on-site to give you a written evaluation. This is rather impossible to generalize without physically being there.

 

[Sponsor]

 

[Nathan-KC]

The reason for the separate drain lines in the 2nd floor bath is to prevent cutting into floor joists. They are only 8 inch deep, and across the distance needed, I cannot get the correct pitch to just tie back into the 4 inch stack without illegally notching/boring joists. Therefore, I chose to run through the joist bays where the lines drop into and then over with correct pitch and then into the wall and down to the basement, eliminating any new cutting into the joists.

The laundry exists in a separate room on the 1st floor (mud room) so it comes in on its own. The 1st floor toilet is about 2 feet from the soil stack and the sink is on the other side of the stack so it just made sense to tie it in separately.

So long story short, the multiple drain lines are to eliminate cutting into structure and the layout of the house.

That being said, with the way it is, it may be overkill in some places, does the overall function work? Are my fittings correct?

 

[Plumber01]

The only thing I found wrong is your 2nd floor tub drain needs to be 2"and the santee on its back for the w.c. should be a combination wye/ 1/8th bend. Not saying things couldn't be simplified to some degree but what you have there will work.

1. The 4 inch cast soil stack utilized a San T on its back to tie the 2nd floor WC to the stack. The WC is within 6 feet of the stack so the stack should act as the toilet vent? Since the stack at this point is only a vent, and the space in the wall is tight, my hope is to replace with a San T again instead of trying to fit a Wye into the space?

You should use a wye. Santee on its back is not code.

2. In the basement, what types of T fittings should I use for the connections of the drains into the soil stack? I assume the 1st floor WC needs a San T because it is getting its vent from the 2 inch vent connection into the top of the Wye section of the stack.

Correct.

As far as the other T connections, does it matter Wye vs San T? I assume it really doesn't matter because all of the lines, apart from the 1st floor WC, are vented before they hit the stack?

Correct. Santee for a fixture drain. Wye or santee for a fixture branch.

4. While I have the walls open, my plan is to run a 2 inch "Future Vent" for the addition of a basement bathroom in the future. You can see the vent in the diagram. My thought is to tie it into the bottom of the stack as shown. When time to add basement bathroom, cut vent above basement fixture flood level and then run venting to fixtures. Remove lower San T, break up concrete floor and tie basement bathroom into 4 inch line running under basement slab. Is this the correct way to plan for this possible future addition?

Correct.

 

[Nathan-KC]

Curious as to why the bathtub drain should be 2 inch? From what I read from the code, a tub/shower combo is minimum 1.5 inch, a standalone shower should be 2 inch?

I agree that should be a Wye for 2nd floor WC, will try and see if I can somehow get that to fit in place of the Sanitary T.

 

[Kreemoweet]

My copy of the UPC allows an 1 1/2 in. trap arm, but rates a tub at 3 DFU, which is too much for a 1 1/2 in. drain, so you'll need a 2 in. pipe after the tub trap. That assumes the DFU for a bathtub has not been changed in code versions more recent that my own, which some evidence I've seen suggests may be the case. [EDITED][EDITEDAGAIN]

You might want to check with your local authorities re the upper sanT. It may be acceptable as a vent connection there, no matter what
the UPC may say. Local rules override any plumbing code provisions.

Vents do not require actual vent 90's, and they cost 5 times what regular 90's do.

You may require cleanouts in the lower horizontal drain piping, if longer than 5 ft.

Your floor sheathing will determine where you need to install notch repairs (i.e. no unsupported edges). If a joist
has been mostly destroyed by a plumber (not at all uncommon), a scab repair is better than nothing.

 

[Plumber01]

You're both correct about the 1.5" tub drain size. Had to look it up it's been so long. I've never roughed in an 1.5" tub drain, I always go 2", most of the time 2" for lavs too. I think I've convinced myself that's code over the years.

You might want to have a shower there in the future anyways

 

[Kreemoweet]

You were correct, plumber01, about 2 in drain required, or at least that was the case for a long time. I had some trouble reading the UPC table, and it seems
there's a typo/misprint in my copy where a note superscript was misplaced on the line above. The bathtub DFU may have been reduced in recent revisions of the UPC. Anyway, we all know
that bigger is better . . .