I removed some indoor/outdoor carpet from a rental. Not real old but pretty
dirty and also some latex paint spots. When you rent its expected that many times you get stuck with cleanups. It was only attached to the floor with a door strip.
I took it home thinking it would probably need replacing. I figured I would try to clean it anyway. I did know that indoor/outdoor has no organic materials when constructed so no matter how much water you apply it will not rot or fall apart or get smelly and it also drops off water quickly.
I used soapy water with about a cup of bleach added to kill bacteria to about 2 gallons of water. Hoping it wouldn't make spots.
I then turn the back side up and applied this mixture to the back on the spots and stains then rinsed them off. I then turned the carpet over and applied it to the top on the spots and stains again. I then used my pressure cleaner with a wide nozzle so not to apply pressure in one place to take the dirt,stains and spots off. It actually removed the paint spots. The carpet look brand new and with the bleach it was disinfected. Really clean and safe to reinstall.
This whole process took only about 25 minutes except from removal.
So if you install a good indoor/outdoor carpet and its not glued down when installed maybe it can be saved if pressure cleaned.
I am thinking of doing this to my patio carpet now.