If an odor in your bathroom just won't go away, check the tank.

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The sources of most bathroom odors are pretty obvious, considering the purpose of this often-windowless space. Accordingly, eliminating most bathroom odors is a straightforward (if not pleasant) task.

But every now and then, a bathroom mystery arises -- a smell that hangs around despite the usual cleaning methods. The toilet bowl is clean. The shower is clean. What's that lingering smell?

You might want to lift the lid on the toilet tank.

Most people don't pay much attention to the tank, but the water standing inside there can trigger smells -- typically musty ones related to mold and/or mildew, which can grow in any consistently moist, closed space. Just ask your shower.

Cleaning a toilet tank is not all that complex, but the ultra-simple method some people use can actually damage certain tank components. So, what to do when you find the tank is the culprit?

First, you ask your co-inhabitants to use a different john for a bit, since this can take a while ...