Okay I know that I found this disturbing and some of you might as well. My wife started pulling up the carpet in our hallway under it is what was nice hardwood flooring. The family pet has used this hallway to relieve himself and subsequently it went through the carpet and pad and has stained the original hardwood flooring. My question is can this be cleaned up or am I going to have to sand it. If I have to sand it I worry that the stains will be so deep--you get the point.

Water stains which are typically black can sometimes be removed with Oxalic acid. ZUD cleanser is essentially this ingredient. I've had good luck with this remedy.

My canine experience tells me you will be sanding. I would still try the advice KISS gave you since its correct. I just have never had acceptable results short or sanding.

Thank you both for your advise I am leaning towards sanding but certainly not looking forward.