These may include the flapper, the tank-to-bowl gasket, and the tank bolt seals.

There are no pipes inside the toilet, but there are rubber parts in the connecting hose and the wall valve itself.

I would recommend against using bleach or vinegar, as they are both solvents and each are able to dissolve certain materials.

if the issue happens again, I'll have to find some help. I never expected to become a plumber.

The gasket between the bowl and tank is often made of a black spongy material, topped with a black rubber ring on the tank side that the flapper seats against.

That part breaks down eventually from chlorine in the water supply (supposedly- I think it's a conspiracy to make you buy new stuff, lol.)

It's a 30 minute job to replace the gasket, if you have the room to get to the tank bolts.

The other piece that is of a similar material are the rubber washers that hold the tank to the bowl.

Once it's drained and dry, try rubbing them with a paper towel- if you get black gunk, you've found your culprit.

eta: I got sniped! What he said ^ !

If it happens again, I'll check into those areas. Wear & time would explain why it has been happening just the last 2 months.

I will occasionally hear a thumpy thumpy sound from the bathroom, mostly mid evenings, by the time I get there no cat is present. I've narrowed down to two. Those two are still quite frisky and playful for being both of them 11 years old. Furoverlords.

When the toilet is flushed after normal use, the air that shoots up carries with it a slew of bacteria and fecal matter that you can't see. This cloud can spread as far as 5-6 feet from the bowl and contaminate everything around.

You did such a great job of cleaning that if weekly additions of a cup of vinegar or bleach to the tank don't stop the black stuff from reappearing, you might need a plumber to check your water lines because no telling where that gunk's coming from. Try this: draw water in a clear glass or bottle from the kitchen faucet at night, let it sit on the counter overnight, then see if it's clear in the morning. That would give you some idea of how far the problem extends. You might get "lucky" enough that you only need to replace some of the pipes closer to the toilet.

is get them a water fountain that aerates the water they drink, something they probably miss once the water in the bowls goes stagnant.

Amazon and pet stores usually have a variety to choose from at various prices.

I have a renal failure kitty who only cares if it's wet, so I haven't had to get one. However, I do know there are a lot of cats out there who won't drink water that's been sitting there for a while.

I live in a small town where the water treatment to me is suspect, I don't know if this is a factor, I am however convinced that it is a lack or influx of too little or too much chemicals, in the morning here I can run the run the water and I get a very pungent smell of chlorine, I use a ionizer to filter, manipulate and ionize the water in an attempt to get better a better drinking experience. I mean just look up water treatment online, theres a list of chemicals used, 14 that I have seen so far and this is just what they are telling us, it's really scary how much control they have over our water and everything else we ingest. Here is just a few used, Algaecides,antifoams, Biocides, coagulants, disinfectants, Oxygen Scavengers, I mean it sounds like a chemistry experiment, I mean we are not dying from the water I guess, at least not immediately, but back to the original reason i'm posting the black ring is basically a mold, although I never experienced it in Charlotte, NC, but here in this smaller town obviously the water is treated differently, but I notice it more on my spare bathroom where the commode is rarely used thus not being flushed daily, I try and make it a point to do this but forget and when I go in there's the dreaded black ring, so to the guy who wrote in about Diabetes, I think it has absolutely nothing to do with your black ring, in my opinion based on what I see here in my home, I also work in Charlotte and never see this in the units at work, I think it is more obvious from city to city or county to county, depending on the water supply and the direct treatment procedures used in waste water, we do in actuality re-use the same water that goes down the drain, kind of gross if you think about it.. Tommy...

Last edited Sun Mar 23, 2014, 06:03 PM - Edit history (4)

It's all good advice- if it's not deterioration of the rubber base parts=toilet to tank bolts and washers='s seals, the flapper and or the toilet to seal rubber base, and because of those things you do not want to put bleach in that tank because it will eat away at the rubber/plastic.And the wax seal or the newer type for that matter.That's at floor level under the bowl where the toilet bolts onto the main drain floor flange.But the bleach no doubt removed some of that so you might wait for the gunk to build back up around the bottom of the flapper or simply replace it now. And if the flapper is worn /deterioration, chances are it is dropping water down into the bowl which in turn drops it down into the drain-it's a gravity thing. That would show up in your water bill, and the flush valve turns itself on and off and you may not be aware of it. There is a test you can do with food dye in the tank for that issue.

People have called me about hearing that flush valve running for no reason than it shuts itself off. I tell them throw some food dye or soy sauce or something in the tank what colors the water than go back in and look at it a few hours later .
If theres food dye or soy sauce in the bowl, than it's the flapper no doubt. Toss in an aspirin in there too ,that el hold it till I get over there to look at it ! Some of them actually have tossed in the aspirin too lol. However the finger test as a rule tells the story, although sometimes it just wears thin and doesn't seal properly. Worn part. I tell them it's a good thing they caught it regards to the water bill as it gets worse.In a home with 2/3/or 4 bathrooms the lesser used ones are the ones that can really run up that water bill. A new fill valve along with the flapper plus the box is only about 10 bucks.5 or less for just the flapper. on edit of course !

If it's the toilet to tank seal going bad as was mentioned- the spongy seal ,on the bottom of your tank you might find evidence of suspect black material as well as moisture leaking so fourth at the bottom of the tank-so you inspect that as well by running your finger around the toiler to tank seal and around where the bolts run through. A flash light is handy for getting a look see.

Someone mentioned run your finger around the bottom of the flapper ,see if residue caused by deterioration is on your finger,also the toilet to tank rubber seals/washers.

If it's in the water supply, you can drain the tank ,after shutting off the water ,stick a bowl or something under the tank where the water line connects ,remove the remaining water from the tank and than disconnect the feed line from the tank and the shut off valve. Than remove the valve and inspect it,looking for a build up of black stuff which will be in the form of hard deposits. you will see build up in the pipes too, thats normal.

If it's there, you simply change out the shut off valve-that will help somewhat.

If it's in the water supply, that's a water treatment issue and they won't give up much information about that.

But it will eventually go away -somehow mysteriously seeming.

Sometimes it's just that pesky flapper in the tank-if thats the case ,simply replace it.
If the toilet to tank bolt washer seals are deteriorated too,you might just as well buy the replacement kit ,has everything you need in it to rebuild the inside of the toilet to tank assembly.
About $30.00 or lest for the kit.More like $20.00 or maybe that was once upon a time !

Good luck with that.