Depth of pipe

I have a 4" pvc pipe from upstairs going into the basement floor. I plan to break the concrete around the pcv pipe to install a 4x4"x3" santee. My question is : Is there a general rule as to how far the 90 degree fitting is below the top of the slab? I know I will have to break the concrete to know for sure.

I would try to have a least 2" of concrete over the pipe when you cover it back up again. Anything less than an inch could easily crack and break out, and especially if a washing machine is nearby.

pipe

The only rule is, "how deep did the plumber feel like digging that day".