I have what are called floating lease options.

What I did with some of my tanks are to put an elbowed 90 degree PVC pipe where the  tank goes to the field- The baffles don't always stop these items from floating under the baffles then getting into the field drain pipe. 

Come to Jesus Talk - I don't know the conversations you have had with him/her, but it's time to be very clear and forceful about their lack of performance and possible poor estimating and diligence in performing per contract details (don't know what they are, but you get the drift!

You can blow down your primary condensate drain line every year and/or install a safety float switch to prevent this from happening again.

@James Wise I use https://cozy.co/  The only drawback is that they pull the rent from the tenant's bank account on the 1st (no earlier) and it takes a few business days to actually get into my bank account so you have to float the mortgage a few days.

As far as an LLC for my long-term rental holds, (and here this drifts into the LLC or not debate), since my LLC would be single-member, I'm not certain it would provide any liability protection anyway.

If you catch my drift. 

Especially with the compliance issues floating about today.

Telling her she has to pay when she likely can't, or would have to move back in because she couldn't float two apartments simultaneously?

I'm looking at vinyl floating floors.