For older rentals this is something I would love to have a plan for, should the water ever stop draining due to a blockage/break/collapse  (or worse- a backup into the house) of an old underground main sewer line. 

I use the California Association of Realtors residential lease, and it has a section under maintenance that reads: “Tenant shall be charged for repair of drain blockages or stoppages, unless caused by defective plumbing parts or tree roots invading sewer lines.”So I wouldn’t see any issue with making the tenant responsible for calling a plumber and dealing with a clog they caused by flushing something that wasn’t meant to be flushed.

Neighbor had a plumbing company come and clear the blockage.

It will also have more blowing power so could shift the lint that's left in the duct and create a blockage that could start a fire. 

Tenant shall be charged for repair of drain blockages or stoppages, unless caused by defective plumbing parts or tree roots invading sewer lines. 

I would tell them they can enjoy this "extra" that most other landlords would exclude BUT as soon as there is a disposer jam, a kitchen sink backup or blockage...I am getting rid of it. 

(Think 2-3 months prior Covid 19 moratoriums attempted to block eviction but unsuccessful before lockdown blockage).I kept “joking” what if the tenant I can’t kick out was using drugs what would happen?

But, that doesn't mean I had the correct mindset for investing & managing my own stuff, a bit of mental blockage there.

While these products may be marketed as a convenience item in this way, the truth is that these types of items have the ability to clog and stop up not only the sewer line on this property, but also can cause blockage and service problems in the public sewer system and pump stations.Unlike toilet paper, these products DO NOT break down once they are flushed.

My preferred plumber would've charged $350 to jet the line.Upon arriving 10-15 minutes after the job began, I confirmed my initial assessment of the blockage.