Why is There Grey Sediment in Your Toilet Bowl?


When you flush and the water starts to swirl, the last thing you probably think about is what’s going on underneath. But if you’ve ever seen grey sediment or flakes in your toilet bowl, it’s time to look a little closer. While this might not be a serious issue, it can be an indication of something wrong with your plumbing. In today’s post, we’ll take a look at what causes this problem and how to fix it.

What is the grey sediment in your toilet bowl?

There are many common reasons why there may be grey sediment in your toilet bowl.

  • Phosphate in water supply – The first reason is that the grey sediment in your toilet bowl is residue from the water supply. Many localities add orthophosphates to their water supply. Orthophosphate is great for preventing corrosion of your hot water heater or pipes, but it can leave a grey sediment in your toilet bowl that may be difficult to remove.
  • Hard water scale deposits – The next reason may be that you have hard water scale deposits in your toilet bowl. This grey sediment in your toilet bowl is actually residue from the calcium carbonate in the hard water scale.
  • City work on water lines – The third reason is that there was work done to your outdoor water lines by the city, and dirt may have gotten in your water supply.
  • Sulfur bacteria growth – The third reason is that the toilet was not used often, which in turn allowed sulfur bacteria to grow in the tank. When the toilet is flushed, the residue in the bowl is often grey in color.

Note: if you are unsure what the cause is of the grey sediment, a professional can inspect your water supply and use a camera to determine where the problem lies.

How do you get rid of the grey sediment in your toilet bowl?

If you know that the sediment is due to phosphate residue or dirt, try flushing your toilet once with vinegar and then follow it up with a clean flush of water. If this does not work, call your local water supplier for assistance.

If the grey sediment in the toilet bowl is caused by bacteria growth, you can do one of two things. First, clean the inside and outside of the tank, and then flush your toilet with a few gallons of bleach water (be careful not to mix it in the bowl as you will create toxic fumes).

Second, if that does not work or is too harsh for you, purchase some bacteria treatment from your local hardware store. Either product will remove the bacteria and leave your toilet sparkling clean.

If the grey sediment in your toilet bowl is due to calcium carbonate hard water scale or sulfur bacteria growth, you can purchase a commercial solvent drain cleaner or scale remover at your local hardware store. Follow the product directions carefully though, as some require you to wait up to 48 hours for results.

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