How is carpet life expectancy determined in California? What would be the life expectancy of a nylon carpet?

I am currently in a back in forth with my landlord over the replacement of a 3 year old carpet. I spilled Drano and left a burn mark on the carpet, which was about 1100 square feet total. Both damages to the carpet were about 2 square feet total. Since the damage was so small, I asked if we could patch the carpet or try to repair it, to which he said no. It seemed as if he would not listen to my requests, so I searched for cheaper carpet companies, and he used one of the suggestions. However, he deducted the full price of the carpet ($1800) from my security deposit. When I told him the useful life rule, he claimed a 20 year carpet lifespan based on warranty. Can we use the IRS Rule of Depreciation for 5 or 9 years of life expectancy?