My tub is backed up with sewage water that doesn't seem to have anything to do with my toilet. It fills up on it's own with disgusting water and drains back out slowly leaving a horrible smell, rocks, sand, and other weird things. I live in a one level studio apt and my landlord isn't picking up or returning any phone calls. What can I do??

My tub is backed up with sewage water that doesn't seem to have anything to do with my toilet. It fills up on it's own with disgusting water and drains back out slowly leaving a horrible smell, rocks, sand, and other weird things. I live in a one level studio apt and my landlord isn't picking up or returning any phone calls. What can I do????
You have a partial blockage downstream from the bath tub. This can be addressed in one of two ways,
1- Pull the toilet and snake the drain line **OR**
2- Remove the overflow and trip lever assembly and snake from there, (see image) here's how to do it.

Unscrew and remove the overflow plate,(The one with the drain lever) and pull out the tub stopper. You now have a clear shot at the trap. The way you were going in through the drain it ran you square into a tee that you can't get around. Now feed the cable( 1/4" best or 3/3" with a small tip. You can rent a Ridgid K50 sink cable.) About 2' down you will run into the bend of the trap. Crank and push at the same time to work around it. Your blockage will be found in the lateral pipe going to the stack. You shouldn't have to put out more then 10 or 12 feet. I have found tub and shower clogs to be mostly hair and the worm should auger into it and pull it back. After you snake pour a few pans of boiling water down the drain. This will loosen the grease and flush the mess out into the main. Hope this helps and thank you for rating my reply. TOM