just moved into my first rural property which is on well and septic. Today I noticed that the upstairs toilet had a weird flat object lying in the bowl that seemed to have come loose from flushing. I fished it out:

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Can anyone tell me what this is and if I should be concerned? I would guess some kind of mineral build up because our well water is very hard. It's brittle and breaks apart easily.

Also, not sure if related but I've noticed that toilet in particular has lots of bubbles "fizzing" in the bowl, particularly after flushing, which I haven't seen before and it doesn't happen in the other bathrooms in the house.

Any insight appreciated, thanks all!

Edit: attaching a photo of where it was. Just lurking, almost out of sight. Toilet appears to be ceramic as far as I can tell.

Also, I noticed taking this picture that I am able to scratch away at the brown stuff starting to accumulate on the bottom maybe the previous home owner was just not very diligent about cleaning...

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  • 1
    What is your toilet made of? Plastic? Ceramic? Porcelain? Can you add a photo of the toilet bowl with a circle or arrow indicating the place where this thing came from? And is there any more in the bowl around other parts of the rim?
    – TylerH
    Sep 22, 2021 at 16:08
  • Is it metallic at all? If there is iron pipe or iron in the water, a magnet will stick to this (or vice versa...)
    – FreeMan
    Sep 22, 2021 at 16:15
  • Checked with a fridge magnet and it doesn't appear to be very magnetic. Maybe a tiny tiny bit but not enough for the magnet to pick up even a small fragment.
    – btown
    Sep 22, 2021 at 17:24
  • Does it fizz if you add vinegar to a small piece of it? If so, it will be calcium carbonate, also know as limescale. Toilet cleaner which says it works against limescale will clean it from the toilet after a few applications - but such cleaners may not be suitable for use with the septic system. Sep 22, 2021 at 17:43

1 Answer 1


It's good old limescale. Absolutely harmless, but unaesthetic.

The easiest is to just pour acid on it which will dissolve it. Vinegar (aka dilute acetic acid) should be safe for your septic tank, it is also safe to use, so pick the cheapest no-name white vinegar available, you'll need about 2 liters. It works faster if the vinegar is hot, just use a cooking pot, but don't bring it to a boil otherwise it will stink. Leave it in the toilet overnight, it should get rid of most of the scale. Then flush with plenty of water to dilute it, and finish the remains with the toilet brush.

If your well water is very hard you'll have to descale a lot of stuff like the kettle, shower faucets, bathroom tiles, coffee machine, etc. Same method.

You can also buy special "anti scale" products which will probably be just acetic acid (aka a bit concentrated vinegar) with a gelling agent and an expensive price tag.

If you're in a hurry, hydrochloric acid works much faster, while obviously being much less safe, and it will tarnish metal. Not recommended.

It works better if there is no water in the toilet to dilute the vinegar.

  • It's vinegar. It's gonna stink from the moment you open the bottle!
    – FreeMan
    Sep 22, 2021 at 18:33
  • My coffee maker recommends running vinegar though every few weeks. Kill two stains with one dose.
    – crip659
    Sep 22, 2021 at 18:51
  • Great, thanks for your help! I've lived with hard water before so I've seen limescale but never at that level! I'll run the vinegar through it like you suggested
    – btown
    Sep 23, 2021 at 1:48

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