I've been noticing puddles of water in the basement on 2 mornings this week. Finally realized the basement toilet has been overflowing after we use the first floor bathroom.

Today I noticed after flushing the first floor toilet that the basement toilet was bubbling for minute.

Then my wife took a shower on the first floor, and the basement toilet started bubbling a lot and then filling up and overflowing.

I assume this is either a blockage in the main drain to the sewer or a blocked vent?

I am on city sewer.

Thanks in advance for any help you can offer!

Time to rod that main line. You could remove the basement toilet or rod from the roof vent stack

Time to rod that main line. You could remove the basement toilet or rod from the roof vent stack

Thanks! What does it mean to "rod" the main line?
I have access to a clean out in the "Y" joint where the basement toilet joins the main drain.
Should I "rod" that? Should I call Roto-Rooter or someone like that?

Thank you again!

Its your choice to call Roto but most DIYers just go rent a electric sewer rodder. Is that clean out cap PVC or cast? I usually drill a 1/8" hole through the cap and have a 1/8" sheet metal screw handy in case I find standing water in the line, if so don't uncap and insert the screw.