How to Prevent a Black Waterline in the Toilet

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Things You'll Need

  • Rubber gloves

  • Replacement flapper

  • 2 replacement tank-to-bowl washers

  • Adjustable wrench

  • Slotted screwdriver

  • Newspaper

  • Toilet brush

  • Toilet bowl cleaner

Leave a toilet bowl without adequate maintenance and care, and you will likely one day notice the presence of an unsightly black line, following the waterline, around the bowl interior. Black lines can also form from the bowl's rim holes, extending down to the black waterline. Once you take the necessary steps to fully clean and remove this black waterline, caused by the buildup of hard water deposits in the water, you must also take ongoing measures to make sure the undesired stains do not reappear.


Step 1

Remove the lid from the toilet tank. Set the lid on a piece of cardboard, where it is safe and out of the way. Twist the toilet's shut-off valve, normally located behind the toilet's left side, completely to the right to turn it off.

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Step 2

Flush the toilet, holding down the handle to allow as much water as possible to exit the tank. Put on rubber gloves to protect your hands. Lift up the rubber flapper inside the tank, and examine it for any deterioration. Rub your fingers over the top and bottom of the flapper, looking for any black streaks smeared on your fingers.

Step 3

Remove the flapper if you find signs of deterioration, including black stains on your hands. Take the old flapper to a home improvement or hardware store, to obtain a compatible replacement. Install the replacement flapper.

Step 4

Examine the black washers underneath the heads of the tank-to-bowl bolts, on the bottom interior of the tank. Look for signs of deterioration, such as if the washers are too soft and slimy, which would unleash black smears into the tank water.


Step 5

Place newspaper on the bathroom floor. Loosen the nuts underneath the tank with an adjustable wrench, while holding the bolt heads steady with a slotted screwdriver, inside the tank. Remove the tank from the bowl, and place the tank atop the newspaper. Replace the washers with new ones, and install the tank back atop the bowl.


Step 6

Place the lid on the toilet tank. Turn the shut-off valve counter-clockwise, restoring the water supply to the toilet.

Step 7

Dip a toilet brush in the water inside the toilet bowl, and scrub inside the toilet bowl, across the rim holes. Scrub around the waterline as well. Flush the toilet. Do this on a daily basis, such as at night before going to bed.


Step 8

Spray toilet bowl cleaner into the bowl on a weekly basis. Allow the cleaner to sit for the specified amount of time, according to the manufacturer's instructions. Scrub around the bowl, across the rim holes and around the waterline, using a toilet brush. Flush the toilet to remove the cleaner.


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