Run an ozone machine for 30 - 60 min (<$100 on Amazon) .  

Sadly, you might need to explain to them how to use a washing machine and how much stuff you can put in it.

Run the machine empty using Finish machine cleaner (I give my tenants a couple and ask them to run it every few months).

A bushhog will do a rough cut , but they can cut tall grass vines and saplings up to 2 to 3 inches depending on the size of the machine . 

I wanted my tenants to assume that when they ask for maintenance a machine responds.

About two weeks ago the Tenant texted me saying the house flooded with raw sewage again, after the washing machine on the second floor dumped water into the sewer pipes.

My property manager did a walk through and said everything looked fine outside of some minor repairs but was advised that the washing machine was broken.

And if she wants an ozone machine, she should pay for one herself, to use in her apartment.

When I purchased the home it came with an older functioning washer machine that has been at the property.

It went from things like wanting me to let them have a washing machine in the unit even though the owner said no to them and after I explained it's because the pipes can't handle it and sorry, I'm not losing my job over it for you (in a very nice way) -- furious reaction, no more friendship.... to wanting me to tell their neighbor to stop having such loud sex (not kidding) and when I said I don't tell other tenants how to have sex (again in a very nice way, while giggling no doubt), I lost that friendship.