In our restaurant we send a lot of things down the drain. Just washing the dishes sends solids and liquids down the drain in large quantities. The dishwasher area has a long stainless steel counter that has a trough that runs the full length of it. The trough terminates at a commercial garbage disposal. Plates are scraped into the trough as they are brought back from customer tables. All of the food waste goes down the drain through the disposal. I use a company that does sewer cleaning in westchester county to keep our drains running smooth.
I have them scheduled to come out on a regular basis to inspect the sewer line with a camera and run a hydrojet sewer cleaner through it to blast away debris. Grease is the big problem. It sticks to the insides of sewer pipes as it cools. Oils that are not solid at room temperature go right on down the drain. Things such as salad dressing move right along. Things such as beef and bacon fat turn solid inside the cool drains and build up. Hydrojetting is a sewer cleaning option that blasts away all the buildup.
The plumbers come in after the restaurant is closed, and they inspect the sewer line first. Then they blast away all of the buildup using the hydrojet tool. They shoot another video of the clean drain. I get to see the before and after look of the drains. Here is the thing about drain cleaning, I have never lost a day of business due to sewer line problems. Other businesses have. The maintenance on our sewer line also keeps me from having to foot the bill for a sudden major repair. Since I own this building my restaurant is in, I pay for everything. I think I would pay for sewer line cleaning even if I leased just to keep things running smoothly.