Then based on @Michael Baum's suggestion, I think I will have my cleaner and/or maintenance person do monthly/quarterly maintenance like using using enzyme based cleaners, grease fighting drain treatments and hot water flushing. 

ARV 900Total reno was 170k Appraisal $399.00 Shut off valves $95.75 paint $300.18 Commeercial enzyme cleaner $72.09 Water activation fee $51.38 shut off valves $38.52 Kilz restoration primer $275.66 Kilz restoration primer $150.33 Shower tile-Master.

I also have a separate septic tank rider that specifically calls out nothing except toilet paper and enzymes can go into the tank.

I would then treat with enzyme (google enzyme for pet urine) usually available at local janitorial supplies.

I recommend looking into enzyme cleaners as well, as they are also effective in removing odors.

Enzymes. 

The sale was not triggered by the urine, but after washing the carpet it is somewhat apparent it had been urinated on, while the carpet was damp the smell got very strong.Professional carpet cleaners use an enzyme-based product for urine. 

It contains the enzymes that, in nature, break down the compounds in the urine, feces, etc.

For one tenant that had a cat (inherited tenant and the only cat I've allowed), I had to soak slab with enzyme cleaner, didn't work well, then soaked in vinegar, replaced subfloor boards upstairs, replace trim all around flooring -- it's a huge undertaking requiring multiple applications.     

The chemicals interfere with with enzyme process.