Toilet in the basement? Bad wax ring seal?

Hub type cast iron main stack? Leak in hub seal?

You're running your sump into a floor drain? Septic system or city
sewer? If city, that's probably against code.

Greetings,

I belong to a little brick bungalow in the midwest, built in
'54, poured-concrete foundation.

Sewer gas smell in basement is detectable, far from overwhelming.

I ran a search, considered numerous possibilities (dry trap, open
clean-out in floor drain, etc). None seem to fit. Sniffed the
bsmt. floor drain particularly carefully as sump, washer, and
AC drain the no odor.

I gotta track it down.

Any ideas?

100% safe to pour a pint or so of laundry bleach in each drain?

Thx,
Puddin'

" ... and the bees made honey in the lion's head."
- from "If I Had My Way", Blind Willie Johnson