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waste pipe for toilet

I want to start by thanking everyone for their help. It has all been very useful and our remodel is going nicely.

Here are todays questions:
I need to put in a toilet that would require a 21' run to the main stack. Is this too long, or as long as I make sure the slope is 1/4"/ ft, I'll be alright?

I have enough room to drop the required 5.25" with only one elbow to reach the main stack. First part of the run is 12', elbow, 9'.
how does this sound?
There are 2 other toilets that join together and then attach to the main stack. These toilets have a vent pipe that goes out the roof. The toilet I will add will connect directly to the stack and not join the run connected to the other toilets.
Does this new toilet need a vent pipe of it's own?

Once again, thanks in advance for the help.

Re: waste pipe for toilet

If I recall 10 feet is the maximum distance for a toilet ( at least around here ) from a vent line.
Chances are you are also going to have other fixtures ..... sink and possibly tub / shower ? ..... which will also require venting.

Re: waste pipe for toilet

it is 6' on three inch to vent or 10'for four inch you will need to vent tis fixture either way and back vent it back to the stack or other properly sized vents to meet most plumbing requirments and mantain proper sanitation within you home. I suggest the use of med or long sweep 1/4 bends on horizontal soil runs , anything over 172degrees needs a full sized cleanout

Re: waste pipe for toilet

You only mention three toilets, but I believe if you have more than that you need to upsize to 4" where the fourth toilet joins.

Re: waste pipe for toilet

I currently have 2 toilets in the house and want to add another bath. With the new addition, my total becomes 3.
We have drawn another option that puts the toilet about 5'- 6' from an existing toilet pipe. This would involve replacing a lot of 4" iron piping. I would change as much as I can to PVC.
Here is my new question.
Is a rubber coupler the best way to go in connecting the new PVC to the iron stack?


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