Black Toilet Bowl Ring - Why?
 

Basic Info.: In Fernandina, built 2012, Nova Filter 3 years, new filters with approx. 4000 gals. used.
We were gone about 12 days, returned to find ugly black toilet bowl ring
in main bathroom. Looked to be some kind of "micro" particles only in that
toilet., tank was clear. Surprised that would happen with the Nova filter.
Any idea what would cause this, and is our water safe to consume ??

What did Nova say?

Google it. Explanations can be found. One cause is a breakdown of the bowl surface allowing bacteria growth.

Probably mold

So, water softener don’t work? I don’t have softener, I have never had that, even after 2 weeks being gone.

I thought OP said Nova system, no mention of water softener

I don't have any chlorine smell or taste after installing our Nova system. I'm not a chemist, but I think the lack of chlorine might be allowing bacteria to develop in the untreated standing water.

I know nothing about Nova.

Black ring sounds like a carbon (charcoal) filter collapsed/leaked into the water.
Should look like very fine black particles.

Definitely won't kill you, but I wouldn't make a habit of it.
___

If you suspect mold/bacteria: Add a cup of bleach while still in there. If bacteria, it will seem to disappear.
(oh, and don't forget to flush your toilet before leaving for any length of time)

We get it and don't have a water filter.

As others posted, it's a biofilm (mold, bacteria, algae, ???)

Try adding a cup of bleach or vinegar to the water before leaving any length of time.

The ring at the water level is an accumulation of calcium deposits that is formed when the water in the bowl evaporates. The mold grows on the calcium ring. Use a pumice stone to remove the calcium from the toilet bowl and you will stop the mold from growing.

I have looked into this. It is likely dissolved Manganese (Mn), and a simple water filter cannot take this out. From my understanding the wells in the villages produce varying levels of Manganese. From 0 to over 12 ppm at the source. I am not sure how many wells there are but I think it is somewhere around 5. As the water travels in the pipes and is exposed to air and chlorine some of the Mn precipitates (goes from dissolved to particulate) and the water softener will take out those particles that arrive at your house but not what is still diluted. As the water takes anywhere from 2 to 6 days to reach any individual home different homes will experience different levels. Our well for Hawkins is at 12 ppm and will forever have that amount. (the well is over a million years old and is 1000 ft deep)
I did a simple test of our water and it contained greater than 1.9 ppm which was the most that test could measure. It only takes .5 ppm to cause black rings. you will also find it in the screens of your faucets, sink traps and the dishwasher. The dishwasher can be worse as the PH level is raised from the detergent and this is one cause of Mn "precipitating". The other is exposure to air and chlorine. If you have a charcoal filter, you may develop strong odors in your sinks and dishwasher as the charcoal neutralizes the chlorine allowing the bacteria that “like” manganese to grow. A slimy substance in the tank of your toilet is an indicator of bacteria as well.
There are very expensive filters to remove Mn and is the same filter used to remove iron. They are called air injection filters and use a venturi to suck in and maintain an air pocket at the top of filter. This causes the Mn to precipitate and fall to the filter to bed to be backwashed out later. The units I have looked at can only remove upto 2 ppm of dissolved Mn and cost between 700 to 1000 or more. Personally, I wont buy a filter until I have my water professionally tested for a period of 30 days. Wouldn’t want to buy a 2 ppm filter when the water coming in has 4 ppm.

Nothing to do with the filters. This is mold from standing water. Clean bowl before you go and/or put some bleach in.

I don't have the problem but was curious, the links below are from YouTube. It seems vinegar could be the solution.

https://www.youtube.com/watch?v=tg9t...l=PapaJoeknows
https://www.youtube.com/watch?v=KsMp...JMGENTERPRISES
https://www.youtube.com/watch?v=TrMd...=CleaningHowTo

It is a mold you will see it on any hardscape you have in your yard also. The Nova filter has a carbon filter as one of the filters this removes the chlorine from the water. The water in the bowl will grow this mold if left unflushed for a period of time. You can add to your bowl something that adds chlorine when you flush to help with this but will still grow if left unflushed for an extended period.

This is the correct answer! I’ve done this on one toilet of ours that doesn’t get used a lot and gets a black ring. The pumice stone takes care of that ring and it stops it from coming back for quite a while.