I have mold/mould in the caulk/grout of my tub. Before I go about re-caulking it, I want to try killing it.

I've seen sources say to use vinegar or bleach but are these sources correct? I've also seen sources state that some mold will not be killed by bleach (they will be bleached instead).

What is the proper way?

2 Answers 2


I have used vinegar many times to kill mold. Spray it on the area where mold appears and let is sit for 15 minutes, then rinse off. Bleach kills surface mold but doesn't penetrate below the surface to kill the "root".

You'll want to remove all the old caulking and then clean the area. Fortunately, vinegar works to remove old caulk, so does alcohol. After the area has completely dried, get a quality silicone caulk and apply it to the seam. let it fully cure, about 24 hours.

  • I do agree with removing the old calking and would recommend using a bathroom calking with mold inhibitors.
    – Ed Beal
    Jul 9, 2020 at 14:42

I think vinegar is better than bleach. Some calking uses acetic acid (really strong vinegar) as the base when it drys out the calk gets hard so vinegar can affect some calking.

I use hydrogen peroxide 3% it is really good at killing mold and fungi, and it won’t stink like bleach or vinegar. Pour it on let it sit , I usually have a gallon of much stronger 30-35% as I use it quite often in Oregon it is a great cleaner. I learned about it when working in a hospital hydrogen peroxide and water cleans and sanitizes with no chemical residue when it breaks down only oxygen and water are left. Hydrogen peroxide breaks down the mold spore and whitens, to get totally white a 7% mixture may be needed, but 3% will kill mold and mildew.

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