Eco Drake Flapper questions

[Mikey]

I installed 2 Eco Drake toilets in late 2016. Last week I heard one of them refilling for a few seconds without being flushed. I turned off the water and waited for a while, and sure enough, the water in the tank had gone down. I checked the flapper valve, and found the rubber(?) seal covered with a light brown grunge (technical term), which apparently prevented a good seal. It cleaned off easily, and after cleaning, the flapper sealed well. I checked the other toilet (used less often) and found the same grunge, but the seal still worked. The water quality is good, and the tanks both looked clean as new. Images show 1,2): top and bottom of a flapper with half of it cleaned, and 3) a tank interior:

This exercise led to 3 questions: 1) What might the grunge be, and why is it so attracted to the rubber seal and nothing else? 2) is there an easy way to remove the flapper assembly from the standpipe (it's very hard to spread the legs of the clips to take the thing off); and 3) can the rubber seal be removed from the plastic carrier and replaced, or does the whole assembly have to be replaced? Looks like the latter; Korky says their 2023 will work.

 

[Jadnashua]

I've never seen repair parts for a flapper.

We like to think that the insides of our pipes and things are immaculate, but that often isn't true. Turn the water off, drain the line, then refill it and look at what comes out! Our small city flushes the mains maybe a couple of times a year, and for the next few hours, the water looks lousy.

 

[Sponsor]

 

[Mikey]

Turn the water off, drain the line, then refill it and look at what comes out!

Every time I do any plumbing work, I have to drain the entire house (bad design, slowly being fixed). Then when I return to normal service, fixtures burp and sputter and cough up a lot of grunge. But this stuff is different, and accumulates on the rubber flapper only -- nowhere else that I can find, so I was wondering why that is.

 

[Jadnashua]

It's hard to say without more info. If you scrape some off, is it slimy? Is it slightly pinkish? The rubber is an organic compound. Fairly stable.

 

[Mikey]

I didn't think to save it for detailed analysis, but it didn't require scraping, just wiped off with a sponge. No pinkishness, just that light brown-with-a-touch-of-yellow color. Don't remember any odor. My first thought was bacterial growth of some kind, and there is some literature in that area. I'm going to just keep an eye on it for now, but I've ordered replacements. If history repeats, I'll have another sample in about a year and a half...