Toilet Flooded Downstairs — Advice

[Sara M.]

My fiancé and are small time landlords. We own two duplexes and do all the work ourselves and both still work regular jobs. Sunday evening we received a text from our neighbors saying their downstairs toilet overflowed and flooded the downstairs. At first, I was said okay no problem we will be right over to fix it. That’s normally how we handle our maintenance issues. We try our best to provide good homes for our tenants in hopes that they treat them and us with respect in return. We don’t want to be slumlords just trying to retire early and build some generational wealth for our son.
This is where things take a turn…..my tenant texts me and tells me that her MIL who lives in the room downstairs, cooks in her bedroom. She does her dishes in the bathroom and dumps all her food waste in the toilet along with wipes. Honestly, not sure why she texted me this because all it did was make me upset.
So I am looking for advice on how to move forward. The toilet is now fixed. But I need tell this lady that the toilet is not to be used as a garbage disposal. What tips on the best way to handle this situation? Should I send them a letter? We live right next door but I do feel better having something in writing.
Their lease is up in July. Would you renew? They really aren’t problem tenants. The son is loud on his videos games and I can hear him yelling on our side. But other than that they enjoy doing yard work and overall don’t cause many issues. I tend to get worked up because to me this is just plain laziness and who knows how much damage she could cause.
I don’t think we are allowed to charge for our time as we are the owners but I would like to bill them for all costs to fix the toilet. And if any flooring needs to be replaced.

[Nathan Gesner]

Quote from @Sara M.:

Your lease agreement should clearly state that the Tenant is responsible for any repairs due to neglect or abuse. Example:

Plumbing Maintenance and Repair Clause. Tenant agrees to use the plumbing fixtures and facilities in a proper manner and for their intended purposes only. Tenant shall not dispose of any substances or materials that may cause clogging, damage, or deterioration of the plumbing system, such as grease, oil, hair, sanitary products, paper towels, wipes, or chemicals. Tenant shall promptly report to Landlord any leaks, drips, backups, or malfunctions of the plumbing system. Tenant shall be liable for the cost of repairing or replacing any plumbing fixtures or facilities that are damaged or malfunctioning due to Tenant’s abuse, misuse, or neglect. Landlord shall have the right to inspect, repair, or replace any plumbing fixtures or facilities at Tenant’s expense, and Tenant shall cooperate with Landlord in providing access and facilitating the work.