Security Deposit and Torn Carpet

[James M.]

What can I take out of a security deposit for dog-destroyed carpet that is 10-years old?

Tenants moved out after 4 years. On top of the normal security deposit, my tenant paid a $400 damage deposit to have a pet. The dog tore through some carpet in three rooms. The three rooms require replacement.

The carpet being replaced is over ten years old (6 years while I was there and 4 years with tenant). I would not have had to replace it if the dog had not destroyed it. I understand that depreciation of the carpet means that it has no value left and I cannot charge the tenant for the damage. 

However, this does not seem "fair" that a a tenant can destroy 400 sq ft. of carpet and walk away scot-free. Can I charge to have the carpet in those rooms replace simply because the excessive damage is the only reason I have to change the carpet?

Thanks for any counsel you can give.