To remove dark water stains from wood floors you have two options.
How to get a black stain out of hardwood floor.
They are usually the result of standing water and are most likely to occur when the finish has worn thin.
Oxalic acid is the best to treat stubborn aged stains discolorations like black water and rust stains from your hardwood floor.
You need to remove the finish to bleach these black stains out of the wood and the best way to do that is to sand the affected area by hand with 120 grit sandpaper.
It should help get rid of a black stain on your floor.
Apply the paste on the stained areas and let it dry completely.
Take 150 grit sandpaper and sand the stain directly again along the grain of the wood.
Allow the mineral spirits to dry.
For very severe stains sanding won t even get them out.
It is best to avoid getting these types of stains as they are difficult to remove but if you already have black urine stains on your wood floors you can attempt to remove them without refinishing the whole area of the floor.
Get a soft or microfiber cloth to wipe the paste.
The result should then be sprayed and wiped onto the exposed surface of the floor.
Soak a cloth in vinegar and apply the vinegar to the stain.
Soak a steel wool pad with mineral spirits and rub the stained area with the pad.
Let the vinegar sit.
In order to create the solution you have to make a mixture of one part bleach and four parts water.
One idea is you may sprinkle a generous amount of baking soda on the urine stain.
Repeat for longer hours if the stain is resistant.
The most troublesome hardwood floor stains are those that affect the wood itself.
Hydrogen peroxide is also suitable for removing the dark stains and the lingering smell on hardwood floors.
Continue sanding until you remove the whole stain.
Use a soft cloth to wipe the paste and luckily the stain will disappear.
Use this solution to scrub at the stains.
Make your own hardwood floor cleaning solution by mixing a cup of white vinegar into a bucket of warm water.
Dip a small brush such as a toothbrush into a small amount of bleach and rub onto the stain.
Mix the vinegar with baking soda to form a paste.
Since urine is acidic it literally burns the tannins in the wood.
Another option is to combine vinegar with baking soda to make a paste.
Soak a piece of cloth in hydrogen peroxide and place over the stain overnight or at least 8 hours during the day.
Adding grapefruit oil to the mix can help with the odor even more.
Sand away the stain with 150 grit sandpaper.