direction of sewer line in basement??

Hi
I used this forum a lot a few years back and completed an upstairs bath reno. Now the basement.
How can I be sure which direction my sewer line is running out of the basement. My main stack is 24 inches off the south basement wall. 15 feet towards the west basement wall I have a clean out ( round cap 2" with a square center for wrench), Going the opposite direction towards the east wall there is nothing visible. My main water line comes in from the west wall. I'm hoping the sewer line would run to the west. two plumbers have told me 2 different things,:confused: Help
Dave, the photo with the abs attached is facing west same direction as my main water line coming in the house. I went to take up the concrete on the east wall and install shower, sink, toilet

Was your house ever on a septic system?

the basement was first built in 37, but has been on the city line for 40-50 years
The ABS you see attached to the cast was a previous owners above ground
( illegal toilet). I am trying to jackhammer up the south wall to the east direction. Why wold you ask about a septic system
Dave

Many times when a septic system is abandoned and city sewer installed they would just connect with the pipe in the back yard and run the drain around the house. This may help you determine which direction the pipe is running.

Call a plumber who has a line locator.

If you want to know exactly where it is running you can call a locating service and they will come out with a snake and locator and can shoot the line and tell you exactly which direction and exactly how deep, to the inch, the line is and can mark it as often as you want like every foot or 2 feet or what ever you want.

I have a clean out about 15 feet towards the west wall as well, it is about 2 feet from the south wall foundation, would that mean my sewer line is heading towards the west wall. 1 plumber said it was heading east,,towards back of house, the other said it was going west towards our front lawn and street. the attached photo is the clean out and it is pointing west along south wall towards front of house, does this mean the main sewer line is running in that direction? After having two plumbers here not sure what to do, I read the two posts while I was attaching the photo. If this clean-out is heading west should the sewer line not be in that direction as well
Thanks Dave

Remove the C/O cap, flush a toilet and see if you can hear the water coming down the stack then watch and see if it goes by the C/O.

Thanks everyone for your help, I feel better already, of course I haven't lifted the jackhammer yet!
Thanks again....
Dave

There is no way to tell which way the drain line runs just by looking at the cleanouts. You have to open them and ascertain which way they flow, and assume that the pipe goes straight from there, which is not always a good assumption.