Hello, I am new to the forum and have enjoyed reading all the valuable knowledge people sharing here. I am planning to build a detached garage about 24' from the house and about 35' to the vertical drainage pipe locates in the bottom of the tri-level in which is about 5' deep from the surface. I assume to add the normal 2' to 4' below that to find the actual pipe. The vertical pipe is 4' size. My plan is to install a new toilet and shower in the garage for which should tie in with the existing drainage from the house. I plan to use the 1/4" pitch per foot formular.

My questions:
1) what material do I use from the garage to run the drainage system?
2) Can the new shower pipe share with the toilet one?
3) What do I need to use to connect to the one from the house?
4) Does a plumber just cut a hole to the cast iron pipe from the house and insert a new one for the connection?

Thanks in advance,

1) what material do I use from the garage to run the drainage system?
I would go for PVC.
2) Can the new shower pipe share with the toilet one?
If you're asking if the shower can connect to the toilet drain the answer's yes. However the shower will have to be vented.
3) What do I need to use to connect to the one from the house?
You will have to cut in a 4 X 3" combination wye and eighth bend In the vertical pipe and run from there to the garage.
4) Does a plumber just cut a hole to the cast iron pipe from the house and insert a new one for the connection?
No, he cuts in a fitting, (answered in #3.)
more questions? I'm as close as a click. Tom

Hello, I am new to the forum and have enjoyed reading all the valuable knowledge people sharing here. I am planning to build a detached garage about 24' from the house and about 35' to the vertical drainage pipe locates in the bottom of the tri-level in which is about 5' deep from the surface. I assume to add the normal 2' to 4' below that to find the actual pipe. The vertical pipe is 4' size. My plan is to install a new toilet and shower in the garage for which should tie in with the existing drainage from the house. I plan to use the 1/4" pitch per foot formular.

My questions:
1) what material do I use from the garage to run the drainage system?
2) Can the new shower pipe share with the toilet one?
3) What do I need to use to connect to the one from the house?
4) Does a plumber just cut a hole to the cast iron pipe from the house and insert a new one for the connection?

Thanks in advance,
Hi Tom,
I found another drainage pipe under crawlspace which I believe the washer and the dishmachine use. I don't think they are as wide as the vertical one which connects to the City main sewer. Can I connect the garage (toilet or shower) to it? If I can, what do I need to be concerned of? Thanks in advance,

Hi Tom,
I found another drainage pipe under crawlspace which I believe the washer and the dishmachine use. I don't think they are as wide as the vertical one which connects to the City main sewer. Can I connect the garage (toilet or shower) to it? If I can, what do I need to be concerned of? Thanks in advance,"

If the pipe's at least 3" and it runs to the sewer you may connect to it. You will still have to vent the shower. Let me know when you're ready and I'l walk you through the venting part. Regards, Tom

Now, in either situations, I would need to dig deep enough below the concrete slab to connect either pipes, right? One would be 7' feet down for the veritcal pipe or 3' feet down for the crawlspace drainage. Or should I cut the concrete from above and refill it later. I can use the 3" PVC to connect to the 3" crawlspace pipe, right? Thanks again,

" I can use the 3" PVC to connect to the 3" crawlspace pipe, right?"
Correct, Let me know what you decide. Tom