Another option is to combine vinegar with baking soda to make a paste.
How to get dark stains off hardwood floors.
Dip a clean toothbrush into the bleach and swirl it around.
In order to create the solution you have to make a mixture of one part bleach and four parts water.
Do a second round after several hours and let the area rest until the next day.
Hydrogen peroxide will lighten the stain with successive applications.
Dip a small brush such as a toothbrush into a small amount of bleach and rub onto the stain.
Then scrub it into the stain using a circular motion.
Soak a cloth and apply to the dark water stain and allow 5 to 10 minutes for it to work.
To remove dark water stains from wood floors you have two options.
Scrub the bleach into the stain with a toothbrush.
The result should then be sprayed and wiped onto the exposed surface of the floor.
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.
Make your own hardwood floor cleaning solution by mixing a cup of white vinegar into a bucket of warm water.
Use this solution to scrub at the stains.
Test an application of hydrogen peroxide in an inconspicuous area of the floor.
Hydrogen peroxide is also suitable for removing the dark stains and the lingering smell on hardwood floors.