Toto Drake CST744 With Black Spots

[l8_night]

Hi Team,

We have three Drake toilets in our home and we love them. The toilets work great but we have developed a black spot issue in two of the toilets along the water line. We have tried bleach, standard over the counter toilet cleaners and in one case a pumice stone (my wife did not know about the danger with CEFIONTECT). None of these traditional methods seem to remove the spots.

We have a whole house filtration system (Kinetico) and are on city water. I am guessing it is black mold but haven't been able to get rid of it. The rest of the bowl is crystal clean. I have attached a couple pictures of what we are fighting. I read some of the existing discussions on black spots but they did not seem to match what we are seeing. Any ideas?

 

[Mikey]

I see a lot of that in our area, so it might have something to do with the water. I see black streaks running down from the rim as well, but the water in the tank is crystal-clear. Lack of regular scrubbing might also be a factor in the bowl, but I don't know how to scrub within the rim, and even in some stunningly clean homes I see the black spots at the water level in little-used toilets.