Hello,

We would like to install a new bathroom (well, half bath = sink + toilet) in our basement. Currently, there is a toilet down there, sitting on a cast iron wye off the main sewer line for the house. We want to move the toilet by approx. 8 feet. The final position would be directly above the main sewer line as well.

What are our best options for roughing in the drains? Should we break up the concrete and hire a plumber to cut into the existing house sewer line (not a task I'd want to do myself)? Should we cut a trench in the floor and connect up to the drain where the existing toilet is?

Also, the existing toilet is not vented, and the main stack for the house is on the other side of the basement. I could probably find a way to run 2" ABS over to the main stack if I had to, but is a vent necessary?

Further information - concrete slab floor, and I'm tall so I don't want to put the toilet on a plinth or I'd hit my head.

Thanks for your advice,

-David

Hi David.

For openers you're not going to be able to place the toilet directly over the sewer main and expect to connect it. You'll have to pick it up with a wye ot combination wye and 1/8th bend.
"What are our best options for roughing in the drains? Should we break up the concrete and hire a plumber to cut into the existing house sewer line (not a task I'd want to do myself)? Should we cut a trench in the floor and connect up to the drain where the existing toilet is?"
Not knowing how the existing toilet was taken off the main and the way the drainage's configured prevents me from answering. You need a plumber to lay the job out and then you can do the scutt work, breaking cement, diging trenches,etc.
"Also, the existing toilet is not vented, and the main stack for the house is on the other side of the basement. I could probably find a way to run 2" ABS over to the main stack if I had to, but is a vent necessary?"

EVERY fixture that has a trap MUST be vented. The bad news is that you can't vent to the soil stack, the good news is that you may be able to do away from running a vent at all. Pick up the lavatory with a tee and install a AAV,(Air Admittance Valve) (see image) on top of the tee.
You will also connect the lavatory drain to the toilet drain so the toilet will be wet vented.

"Further information - concrete slab floor, and I'm tall so I don't want to put the toilet on a plinth or I'd hit my head"

There is no reason for you to have to platform the toilet. Goods luck, Tom