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About to re-do toilet % shower pipe

2024 Views 20 Replies 6 Participants Last post by  TheEplumber
Hi All,

In the pictures shows what I currently have. Cast Iron, what looks to be 4 inches.

I plan on insulating and framing everything out and had a question.

Space from wall:

-- 2" XPS on wall
-- 1/2 gap for any bow
-- 2x4 framing
-- 1/2 drywall

I'm at 6.5 inches from where the finished wall will be.

For the toilet -- Do I come off the the wall now 19.5 inches for the toilet? 13" + 6.5" = 19.5 I believe the toilet needs to be 13" off the back wall?

For the shower pan -- Do I find out what size pan I want, use their measurement and added it to my finished wall (6.5")?

The rough in will all be covered by concrete so I need to get this right.

Tips, pointers, suggestions all welcome. I'm looking to do this this weekend.



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Toilet stub(center) should be 12 1/2" from studs--12 from finished wall surface

Shower ----pan is mounted to the studs---get the specs from the manufacturer---

leave a 10x10 boxed in opening for the shower stub to give you some adjustment---

most times I will leave that area open and add the P-trap at the time of the pan installation--then pack with gravel and add a
thin skin of wet concrete as I install the pan---
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Thanks Mike!!

One last question. I didn't take any pictures of what the shower pipes looked like and as you can see in Picture 1, its just a PVC pipe sticking up.

Since there will be a toilet behind the shower drain, what would a P trap look like? I'm assuming I'll have to offset it from the main pipe so the P can fit.

Do you have a pic of what it might look like as well?
While that's all open get rid of that old drain and replace with PVC, at some point it is going to leak, cause plug ups and collapes.
That plugged up T is the vent---that is needed and must be a 2" pipe,within 5 feet of the toilet--

The shower drain will also be 2" and must come off the main using a Y fitting.

easiest and best method ,as Joe suggested, would be to cut the old iron pipe just to the right of the vent T--use a rubber Fernco boot to convert to PVC.

Iron is easiest cut by renting a chain breaker--snapper----wrap the chain around the pipe--hook it into the tool and turn the crank--POP--done---
Im with Joe. Get rid of that pipe up to the Y, install PVC in a bed of sand and add vents drains and a cleanout.
I don't know why, but I'm having a hard time visualizing this. If anyone has time, could you do a quick Paint sketch of how the toilet, shower and vent would be laid out?

If you dont have time, no worries. I appreciate the help either way.
Where is the sink going to go?

If you could make a sketch showing the approximate locations--we can guide you---

Include the location of the old pipe,too.
Thank you for the willingness to help me!

First picture shows where the sink will be. It will be next to the ABS with the white PVC coming off. This is where the sink was before as well.

Also, I found pics of the shower before I tore it out.


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Don't know your exact layout but this might get you started. UPC states a toilet vent must be within 6ft. A trap arm for a shower is max. 5ft. Of course- it can be angled whatever directionb you want. I drew it at a right angle for clarity
There are a couple of other possible layouts too


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Thanks for the drawing!!

Now that it has to be 12 inches from the back wall. How far does it have to be from the side wall? Is that 15 inches in both directions?
Can someone tell me if this will be OK? I'm primarily concerned with the location of the 2 inch vent. Can I put it behind the shower drain as in the picture?


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According to my code, heres how I rough-in.

13 from unfinished wall to the centre of the flange
15" from any objects to the side for clearance (tub, wall, etc)

Can you take one of you pictures and update it to where the fixtures will be located? The way that you have it there would be illegal by my code in Canada-but its very similar to the US code
This drawing is really crude. Shows a sink, toilet, shower and vent. The distance from the toilet to the shower will be about 4-5 feet (hard to tell from the picture).


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I have a few questions again...

Which of the 4x2 connections should I use for the drain and the vent? (First 2 pictures)

In the 3rd picture, I layed out the pipe in this order. Elbow for the closet flange, 2" vent, then 2" drain. Is this proper venting for both toilet and shower drain? If not, please let me know how I need to set this up.



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I hate bumping my posts, but I would love to have someone chime in on my issue.

Let me know if you need more information or more pictures!

Can someone tell me if this will be OK? I'm primarily concerned with the location of the 2 inch vent. Can I put it behind the shower drain as in the picture?
I gave you an illustration of an acceptable venting method for my code- the common vent is positioned to vent both fixtures. Your illustration would not pass my code standards because the vent is laying flat plus it is only venting the toilet. Would it work? I don't know.
Sorry, I did see your post, but was curious if a single vent would work, like in the drawing i added. Now I know it wont.

By your drawing, it looks like my materials would be:

1 4" PVC pipe
1 4" x 2" wye
1 4" x 4" x 2" x 2"
1 2" pipe (I can cut to length)
1 P trap assembly
1 90 degree long sweep
1 closet flange
1 4" furnco (connecting to cast iron)

Does this sound about right?

Also, does the Furnco need to be fully shielded or can it just have 2 straps if its going to be buried?
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I've labeled the fittings for you-
When connecting plastic to cast iron inside the house, I like to use a shielded 4" cast iron x plastic coupling- code in my area. Others use a 4" fernco. Be sure the pipe has the outside scale removed or your seal won't be water tight


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Thank you!!

Where the pipes have a 4 way intersection, what is that piece called? A 4x4x2x2 sanitary cross?
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