I am asking this question again - didn't get a answer last weekend.

I am considering adding a Basement half bath. I realize this is no minor undertaking. I have the venting designed, and luckily have a wall chase nearby to accommodate that. My question is about locating the existing sewer pipe under the basement floor so that I can tie into that. I know where the main stack clean-out is. There is another toilet stack from an existing 1st floor toilet across from where I would like to install the new toilet and sink in the basement. These stacks are cast iron, as such I would assume the pipes under the floor are also cast iron. Ideally, I would think that the sewer pipe would cross under the concrete floor nearby where I would tie into it. How can I be certain the pipe is where I think it is. Are there locators, or locating methods I could use? I don't want to cut into the floor and find out the sewer pipe is not where I thought it would be.

Appreciate your help.
Thanks,