Bio-Clean is what I'm using.
The stuff is so safe, you can eat out of the container, and yet it gets rid of the grease in the pipes.
It won't be eating the bottom of your pipes
If the lines are plugged up, you still may need to snake the lines, or if you have hair in them.
It takes time for the product to work.
Cathy was using this in her home for a few days, and when I went to snake her downstairs lav drain, the snake came back totally clean.
The city of Bellevue requires something like this for restaurants with grease, especially the KFC on Main Street.