Grease in garbage disposal - blocked drain
I share a room in an old house. In the first few weeks I put no more than 1/2 cup of grease in the garbage disposal and chased it with hot water.
The sink has 2 basins. Now when we run water in either one, the water came back up the other - much dirtier than it went down.
The landlord says that my little bit of greased caused this problem. I suspect that the blockage has accumulated over time - a time much longer than I have been in the house.
There's a washing machine directly under the kitchen which drains into a basin as well. It drains slowly but otherwise seems to work well.
Who do you think is correct?
How to clear the blockage?
Thanks!