Let’s start with the list of things that can be flushed down a toilet.

Human waste. Toilet paper.

That’s it.

A toilet isn’t a hole in the ground, into which anything disappears with a pull of the lever. And just because you can flush it doesn't mean you should: Items like tampons and wet wipes don’t disintegrate in water but instead accumulate in the sewer line, which could create a backup all the way to your toilet. (That's when Overflow Protection comes in handy.) Clearing the blockage could require a plumber to remove (or even replace) the toilet.

For clear pipes and a clean environment, keep these 10 things out of the flush zone.

1. Moistened wipes

Toilet paper is made to disintegrate when wet; in fact, it contains more water than it does paper. Pre-moistened wipes? Not so much. Wipes—even flushable ones—stay intact when flushed and can build up in pipes.

2. Feminine products

After being flushed, tampons continue to absorb water, swelling up to four inches in diameter. Same goes for maxi pads.

3. Cotton products

Cotton balls, cotton rounds, cotton swabs. You guessed it: They don’t break down, either.

4. Medication

Never send medication down the toilet to the wastewater treatment plant; that’s how traces of pharmaceuticals end up in drinking water, lakes and rivers. Visit disposemymeds.org to learn how to safely get rid of medication.

5. Dental floss

Not even the slimmiest of bathroom products is safe for sewers. “If everybody on the street flushed all their dental floss, imagine the wad of floss that would accumulate,” says Jeff Morgan, owner and president of Morgan Miller Plumbing in Kansas City, Missouri.

6. Anything latex

Just don’t.

7. Unclogging chemicals

Clog-busting chemicals are meant to clear hair from a drain, not unclog a toilet; they’re harsh enough to strip porcelain from a toilet—and even melt pipes. Mother Nature doesn't like them, either: You wouldn't pour drain-clearing products in a lake, so don't pour them in your toilet.

8. Kitty litter

Combine kitty litter and water and you’ll get something like concrete.

9. Toiletries, jewelry, your cell phone …

Don’t use your toilet’s tank lid as a storage shelf. If something falls into the bowl and gets flushed, call a plumber: He may be able to retrieve it from the trap underneath the toilet before it travels further down the pipe.

10. Underwear

It sounds crazy, but Mont Stephenson, general manager of Brewer Benjamin Franklin Plumbing in Phoenix, has seen it. After something embarrassing happened, the suspect tried to flush away the evidence. “That thing is not a trash compactor,” says Stephenson. “It’s a toilet.”