Hello,

My toilet continues to be backed up after several attempts with a plunger. When I turn my sink on bubbles start to form in the toilet bowl.

Wondering if you could diagnose the problem and recommend what I should do?>

Thanks

Sounds like you have a clog in your drain, likely right near the vent stack. If it is safe to get on your roof you should rod down the vent. Go the jeight of the house and then 10' more. If you can't go to the roof, look for a clean out or if you must remove the toilet and rod the 4" pipe.