I’ve been in the wood floor business for over 20 yrs.. It really depends how deep the urine has penetrated into the wood. I hate to tell you this, but you will probably need to replace the wood, the acid in the urine will discolor (usually turns very dark if not almost black) the wood as deep as it has penetrated. If it hasn’t penetrated too deeply, you may able to sand it out, but it will take more than a "light sanding," and you should always try to sand the stain out before doing any replacing. Unfortunately there are no commercial products that will take the stain out, and be careful using bleach. Unless, you are an expert at matching wood stains and finishes, it may be best to hire a hardwood flooring contractor, sorry for the bad news.
I just got done helping a neighbor re do his oak floors and he had 3 stains from cats…worse than dogs. Anyway we used pool shock (concentrated powdered chlorine bleach) after trying steam, oxalic acid, deck bleach, household bleach, sanding, and just about every other "trick" recommended. The shock bleached the wood color out completely and the stain. We went back over it with some stain to regain the color (not prefect but you couldn’t really tell) varnished the whole floor and then polyurethane it..it looks like it was just installed it came out beautiful. Keep in mind this was a very bad stain as another post mentioned the wood was black from the stain.
Also we mixed the shock with just enough water to be like a runny paste and painted it on..Be careful this stuff makes some POWERFUL fumes if you thought the oxalic acid was bad this stuff is a hundred times worse. Good luck
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