How to Clean a Toilet Tank (the Part Nobody Cleans)

Step by step

1. 1

   Set the lid down safely

   Lay an old towel on the floor and set the tank lid on it, flat side down, out of the way of your feet.

2. 2

   Turn off the water

   Find the small valve on the wall behind the toilet, near the floor. Turn it clockwise until it stops, which is the direction Fluidmaster gives for shutting the water off.

3. 3

   Flush and sponge it dry

   Flush the toilet and hold the handle down so most of the water drains out. A little water stays in the bottom, so soak it up with a sponge and wring it into a bucket. Fluidmaster’s own repair steps start the same way: flush out the tank and sponge it dry.

   What it looks like: an empty tank with a bare floor, so you can see any crust, rust-colored stains or slime.

4. 4

   Scrub with dish soap and warm water

   Put on your gloves. Add a squirt of dish soap to a bucket of warm water, dip your brush, and scrub the tank walls and floor. Work gently around the valves and the seal rather than scrubbing hard on them.

   What it looks like when it is working: the slimy film comes away on the brush and the porcelain underneath looks clean.

1. 5

   Wipe the seal and look at it

   Wipe the rubber seal gently with a soapy sponge, and take a good look at it while you are there. Fluidmaster says a seal that is damaged or dirty lets water dribble from the tank into the bowl, and that is what keeps a toilet running.

2. 6

   Turn the water on and flush twice

   Turn the valve counterclockwise to turn the water back on, and let the tank fill. Flush twice to rinse away the soap, then set the lid back on carefully.

   What it looks like when it worked: clear water sitting in a clean tank.

When it will not work, and what to do instead

Sometimes the tank gets dirty again fast, or the toilet acts up after cleaning. Here is what that usually means.

• You heard the blue drop-in tablets keep the tank clean for you. A tablet you drop in and forget sounds like less work. But Kohler’s toilet manual says not to use in-tank cleaners, because products containing chlorine can seriously damage the fittings and cause leaks. Fluidmaster says the same, and both say tablets void the warranty.
• There is hard white crust on the walls. Soap and a brush will lift slime, but not mineral crust. We could not find a toilet or parts maker that gives a safe way to dissolve crust inside the tank, and the CLR label rules out plastics and brass. So scrub off what comes loose and leave the rest.
• The slime is orange, reddish brown or dark and comes back fast. On a private well, that can be iron bacteria, which Penn State Extension calls more a nuisance than a health hazard. The University of Nebraska says to test your water, and warns chlorine may make the staining worse.
• The toilet keeps running after you clean. The seal may be worn. Fluidmaster calls replacing the seal a simple job that can often fix a running toilet.
• The ring is in the bowl, not the tank. See How to remove a toilet bowl ring.

Why it works

A toilet tank holds the same water that comes out of your pipes, and it sits still between flushes. Well water with iron in it can feed the bacteria that make orange or dark slime, and that slime settles right on the tank walls.

Soap and a brush lift that film off. Think of a flower vase you never empty. The water looks fine from the top, but tip it out and the bottom tells the truth.

The tablets look like a shortcut, but Kohler says chlorine products can seriously damage the fittings inside the tank. A soap and brush scrub does the job without putting those parts at risk.