I am adding a bathroom in my basement. I have searched and read quite a bit of postings in the plumbing section of this website and came up with a plan on how to proceed. I have a few questions and also would like to present my ideas I came up with after reading old postings and have someone tell me if my ideas are going to work and/or if I should do something different. I have attached an AutoCAD drawing to help illustrate my ideas. The numbers in the drawing ‘Proposed Layout’, 1-6, represent the various visible parts of the sewer system in my basement. 1. Clean Out 2. Main Stack, everything upstairs drains into this stack except the kitchen sink. 3. Stack in which the upstairs kitchen sink drains. 4. Stack which utility sink in the basement drains, then goes by #2 (not connected) and goes up into a wet wall for the upstairs bathroom and makes a vent loop for the bathroom fixtures. 5. Cast iron floor drain. 6. Cast iron floor drain.

SIDE NOTE: The drawing is to scale, however the location of the shower drain is not exact, but is close enough for what I am trying to figure out.

Questions
1. By looking at the file ‘Proposed Layout’, is it safe to assume the sewer line runs in the side of my house by the cleanout (#1) then goes directly over to #2, then to #3 and #4?
2. I examined #5 (floor drain) and it seems to angle back to main stack, #2. Does this seem to make sense? At first I thought it would go back directly to #4, but after feeling around the bottom of the drain with a coat hanger, it seemed the trap angled back to #2. The green line connecting #5 to #2 is the path I believe the drain takes.
3. The floor drain is a 3” drain, can I tie into this drain for my bathroom fixtures?
4. If I can tie into the 3” floor drain branch, does the layout seen in the file ‘Proposed Layout’ seem to be a good layout? Is everything vented properly? If this isn’t a good layout, could you please sketch me one that make more sense?
5. If I can tie into the 3” floor drain, would the proper way be to use a hubbed 3” wye and add short pieces of 3” pvc and then connect to the cast iron floor drain with hubless band clamps?
6. Currently there is a utility sink which drains into #4. #4 Then travels up to the ceiling and over goes over by (not connected) #2 and then up into the upstairs bathroom wet wall and makes a vent loop, connecting up with other vents and ties into the main vent stack. In other words, above the utility sink drain, #4 is a complete dry vent which eventually gets to the main vent stack. Now the question. Can I move the utility sink from #4 over to #2, tying the drain into #2, and venting the utility sink and new bathroom through the vent the utility sink used to use (#4)?
7. Should I use a 3” or 4” flange and closet bend for the toilet?

Since I do not know what other plumbing or where it is I will only address the current drawing. I personally would use a 4" pvc riser for the toilet and a 4 x 3 floor flange glued inside the 4" pipe. The toilet drain can still be 3". I would also relocate the wet vent from the toilet branch to a place between the toilet branch and the floor drain #5. this way #5 is still vented.
When connecting pipes of different sizes a nohub is not best. I use a fernco [black rubber sleeve with 2 hose clamps]. The cast iron is slightly smaller than the pvc.

1. By looking at the file 'Proposed Layout', is it safe to assume the sewer line runs in the side of my house by the cleanout (#1) then goes directly over to #2, then to #3 and #4?

It looks that way, however, The one thing I can tell you is that it's not safe to "assume" anything in plumbing.

2. I examined #5 (floor drain) and it seems to angle back to main stack, #2. Does this seem to make sense? At first I thought it would go back directly to #4, but after feeling around the bottom of the drain with a coat hanger, it seemed the trap angled back to #2. The green line connecting #5 to #2 is the path I believe the drain takes.

You're "assuming" again.

3. The floor drain is a 3” drain, can I tie into this drain for my bathroom fixtures?

Our codes mandate a 4" drain line for the toilet under the cement and 3" above the pour. Check your local codes for this.


4. If I can tie into the 3” floor drain branch, does the layout seen in the file 'Proposed Layout' seem to be a good layout? Is everything vented properly? If this isn't a good layout, could you please sketch me one that make more sense?

It looks OK to me. The shower will be wet vented by the lavatory vent. Oops! You don't show a lav vent on the drawing. You were planing on venting it weren't you?
I also need to know which way the sewer exits the house and where.

5. If I can tie into the 3” floor drain, would the proper way be to use a hubbed 3” wye and add short pieces of 3” pvc and then connect to the cast iron floor drain with hubless band clamps?

I would cut in a cast iron NO-Hub wye, secure it with No-Hub couplings and then convert to PVC off the branch of the wye.

6. Currently there is a utility sink which drains into #4. #4 Then travels up to the ceiling and over goes over by (not connected) #2 and then up into the upstairs bathroom wet wall and makes a vent loop, connecting up with other vents and ties into the main vent stack. In other words, above the utility sink drain, #4 is a complete dry vent which eventually gets to the main vent stack. Now the question. Can I move the utility sink from #4 over to #2, tying the drain into #2, and venting the utility sink and new bathroom through the vent the utility sink used to use (#4)?

You wish to change the entire configuration? Sure you can do that. IF you run a separate vent for the utility sink but what about the illegal "S" trap you built by not venting the group off the lavatory? A much better way would be to vent the group off the lav and then revent the lav back to dry vent#4.

7. Should I use a 3” or 4” flange and closet bend for the toilet?

It depends upon whether local code will let you run 3 inch under the slab.
Good luck, Tom

The current code for a toilet allows 3" by fixture units for toilets. it used to be there was a question, and may still be, how many toilets can you put on a 3" waste line? So many missed that question. It was on the journeyman test and on the masters test. Everyone knows that a 3" pipe can carry 2 toilets and ya gotta go 4" for 3 and up to 52 toilets. The code has changed. It now goes by fixture units. On page 57 in the sbcc code book it shows a 3" line able to carry 36 fixture units. On page 56 it shows a private toilet has 3 fixture units if it is a 1.6 gallon toilet and 4 fixture units if greater than 1.6 gallon per minute [gpm]. Which translated now means you can put 12 toilets on a single 3" line if they are 1.6. and a 4" line can carry 180 fixture units. This means you can put 60 toilets on a 4" soil line. i would not do it, but legally you can. by the way, on the test, the answer is none. you can not put any toilets on a 3" 'waste' line. It has to be a soil line.
As for the drawing, I would run my horizontal for the toilet in 3" and the vertical [riser] in 4".

Tom,Doug238
Thanks for the reply. I apologize, I left out the fact that I was venting the bathroom through the lavatory by connecting it to a vent from the utility sink (new location) and tying into the vent from #4. No S trap. The area where the utility sink is currently located will become a finished area and I want to move the utility sink to #2 to make a unfinished utility room. And to answer your other question, the sewer exits the house out the right side of the drawing by the clean out.

Thanks again Tom and Doug. I certainly appreciate the help, it must take a lot of time to go through and answer all these questions... thanks for the time you put into this.