What's the No. 1 Thing You Shouldn't Flush Down the Toilet?

The answer may surprise you.

Every day we flush away products without thinking, but how is that impacting our water systems?

Popular Science magazine's Amy Schellenbaum says we should think twice about the items we're putting down the toilet, however innocuous they might seem.

"A lot of people consider their toilet like a garbage can," she said. "They think if it flushes you're good to go. That's not the case." 

First up: dental floss. "You figure this is small enough, right?" Inside Edition's Steven Fabian asked.

"No, don't do it," Schellenbaum said. "It's just not an organic product that's going to break down."

Similarly, you might think Q-tips don't pose a problem, but they're too stiff to flush. "They will not turn into liquid in your system," she said.

Contact lenses should also not be flushed. "Big no no," she said. "They're made of plastic. Putting plastic in our water system is never good."

And don't flush prescription drugs, which are contaminating our rivers and oceans, or feminine products.

But the No. 1 product to avoid flushing down the toilet? Wipes.

"These ones even say flushable," Fabian pointed out.

"They're called flushable wipes only because they leave your plumbing but that doesn't mean there aren't effects downstream," she said.

When you flush items like wipes, they end up in one of the many sewage treatment facilities across the country. Eighty percent of the products collected at New York City's largest facility are wipes.

"A lot of these are materials that we just can't treat," said facility manager Frank Loncar as he pointed to the waste. "They shouldn't be flushed down the toilet."

Schellenbaum says you should only flush the 4 Ps: "Poop, pee, puke and paper," she said, adding: "Toilet paper only."