Bathtub Sloping Issues

[Dan Short]

Hi Chicago Investors,

I'm fixing up my Lincoln Square 3-flat and noticed a sloping issue today with all of my bath tubs. Has anyone run into this before or have any tips how to fix?

All 3 bathtubs are older and are pooling water instead of draining because the base of the it looks has sank to a lower point than the drain. It is causing discoloration and before I can rent it out will need to have a tub that drains properly. See photos below.

Is there a way to fix this without pulling out all 3 tubs and replacing them? 

Thanks for your help!

Dan Short