Soil line question

[RickAZ]

I'm remodeling my master bath. The home was build in 1976. I'm in Tempe, AZ. The current soil line plumbing has a 4" to 3" elbow connecting to the 3" outbound line. I'm relocating the toilet and will be able to maintain a 1/4" per 1' slope. Although I've read that 1/8" is acceptable as well.

After spending some quality time at my local big box store buying parts, I have a few questions:

1) Is there an advantage in the existing 4" to 3" configuration? The only advantage I see is that the flange sleeve can slide inside the 4" pipe resulting in less disruption of the flow.

2) Is 3/16" adequate for the slope or should I make it 1/4"?

3) Should I be concerned about having a 45 elbow in the run beyond the 90 attaches to the flange down pipe?

4) My existing plumbing is ABS. Should I continue with that or adapt PVC for the new work?

5) Are there any gotcha's that I need to be aware of?

Thanks you in advance. This forum has been a great reference for me.

Rick
Tempe, AZ

 

[Reach4]

Is there an advantage in the existing 4" to 3" configuration? The only advantage I see is that the flange sleeve can slide inside the 4" pipe resulting in less disruption of the flow.

1. That fitting is called a closet elbow. You can have an outside 4 or inside 4 flange with that.
2. IPC allows as shallow as 1/8 per foot for 3 inch, so 3/16 is adequate. It doesn't seem adequate for big solids, but neither does 1/4, right? Yet they work. That said, with a toilet, unlike the trap arm for a tub, shower or lavatory, the exit from a toilet can go steeper down than 1/4 per foot.
3. I don't picture what you say, but 45s are not usually a problem.
4. It is usually best to continue with whatever is in use. What is predominate for drain piping in your store? If ABS, and you have ABS already, stay ABS. White slip drains and traps are usually not PVC. You can change material there, because you are not gluing.
5. Get a nice flushing toilet. Consider putting a GFCI outlet for a future bidet seat. Strongly avoid drilling porcelain.

 

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[RickAZ]

3. I don't picture what you say, but 45s are not usually a problem.

Thank you for your feedback. I probably should have written #3 better.

3. For the horizontal run, I'll need to add a 45 to connect to the 3". I'm hoping this will not pose an issue. I've read some conflicting posts as to whether that is a problem or not. I will make the soil run a 1/4" per foot drop.