Every time I flush my main level toilet it backs up my basement sewer drain.

The basement toilet flushes fine as does every other fixture in the house. The backup is only small and recedes immediately. I have turned on every faucet and ran a hose full open to the drain in question while dumping a full bathtub of water all at the same time and nothing, no backup. One small flush and it guarantees a backup about 4 feet around the drain and again it recedes instantly.

I have snaked the toilet as well as the troubleshooting I have mentioned above. I am assuming the venting is fine because all drains run just as quick as before the problem.

I do have a concern. The city has been working on a major sewer line change for the past 2 months about 8 blocks from my house but this just started yesterday.
Any help would be GREATLY appreciated.
Thank you so much in advance.

You have a partial blockage downstream from the basement floor drain. The solution would be to snake from the floor drain. Run out about 15 feet of snake and then try flushing again. Does it work better now? Let me know, Tom

You have a partial blockage downstream from the basement floor drain. The solution would be to snake from the floor drain. Run out about 15 feet of snake and then try flushing again. Does it work better now? Let me know, Tom

Thank you for your reply.

I am getting a snake today... Had so much to do to prepare in case of any mess I wasn't able to do it yesterday. At least when all is done my basement will be clean :)

Thank you so much for the help... I will reply when I am finished tonight. I hated to rent a snake and then not be prepared in case I had to go through the other cleanout which is in a finished play area for my kids.

Have a great day!

Btb