Kohler Toilet mold problem :Anybody know how to get black mold out of the rim. Leaves black streaks in bowl. Has tower type flush valve.

 

Generally a weekly cleaning with toilet bowl cleaner is all that is needed to keep mold at bay. There are also tablets that can be dropped in the tank, although most plumbers dont recommend you use them constantly as they can harm parts.

You might get a few tips from this guys video, as often the problem is that you have internal mold growing in the rim of the toilet that scrubbing and cleaning alone cannot get to.

 

Flush the toilet twice, just before the second flush turn off the supply valve and hold down the flush lever until the toilet tank is as empty as possible.

Make up two gallons of either bleach or vinegar of twice the strength recommended to kill mold. DO NOT mix the two materials or other materials (besides water) together.

Pour that into the toilet tank.

Flush the toilet holding the lever down so the solution goes down as fast as possible and then the toilet tank is as empty as possible.

Wait fifteen minutes. Then turn the toilet supply on again and call it a day. If it does not look satisfactorily clean then wait a day before trying again.

The importance of a fast flush with a lot of solution is so most of the bore of the channels in the toilet bowl rim gets occupied with solution. Flushing only a little at a time will result in only the lower edge of the bore getting wet leaving mold a little higher up not touched by the solution..

 

Alternate method of sanitizing the channel or bore inside the bowl rim. Uses much less cleaning solution, perhaps a quart.

Use duct tape to cover up all except one frontmost hole under the rim, The tape will stick better if you wash and dry the underside of the rim well.

Find a soda straw that fits into that last hole but not terribly loosely. Snip the end of the straw at a 45 degree angle. Insert the snipped end into the hole under the bowl rim as far as possible gently and seal as best as you can using narrow strips of duct tape. Snip off the exposed end of the straw leaving about an inch.

Pour in the desired solution until some comes out the soda straw. Use the overflow tube in the middle of the toilet tank; do not flush the toilet. Wait an hour.

Uncover a hole next to the soda straw just long enough to let the solution or rinse water out. Pour in water to rinse out the inside of the bowl rim before trying a different cleaning solution.

(Remove all the duct tape when done.)

 

All good solutions, but the most practical is a regular cleaning with a brush once or twice a week. If it's persistent don't leave liquid waste standing, flush every time.