Airplane “lavatories” are usually just a small step up from, let’s say, the Porta Potties on day two of Coachella. In other words: pretty gross most of the time. But also, an essential amenity for anyone who flies and/or appreciates in-flight cocktails.

But what do you really know about the lavatories on planes? Or what should you know. Well, to start, the word lavatory is derived from the Latin “lavare,” which means: “to wash” (not larvae like the bugs, although more on that below!). Makes sense, as you are (hopefully) washing your hands.

Also, all of this other really fascinating stuff, which will probably forever change the way you look at the bathroom on your next flight. But won’t actually stop you from using them. ‘Cause, of course, you still love cocktails.

There’s no rule that requires airplanes have a working lavatory

Seriously. The FAA has requirements about pretty much EVERYTHING, but there’s nothing that says commercial planes have to have a bathroom. In fact, a 2015 flight from Westchester to Chicago last year took off despite the fact that the only lavatory was out of order, which meant everyone had to hold it for two-and-half hours.

Snap Happy/Shutterstock

Most of the first toilets on planes were buckets

Yup, if you needed to go, you did so in a bucket with a lid. Although a British flying boat in 1934 had a toilet that opened directly to the outside, because what could possibly go wrong with that system? Well, at least one thing: when the lid was lifted, the airflow caused the toilet to make a whistling noise that earned it the nickname “The Whistling Shithouse.” Also, flying poop: never a good idea.
 

Luckily, blue ice poop no longer falls from planes

Because it’s not a good idea to have a bowl filled with water sloshing around during turbulence, airplanes eventually put in actual chemical toilets that used Anotec, a blue deodorizing liquid, and transferred waste into storage tanks on the plane. Fresh fluid circulated with every flush though, so this meant that planes had to carry hundred of gallons of Anotec on every flight, which increased fuel consumption. Way worse than that though: the systems would sometimes leak, and sometimes those leaks would escape the hull, and long story long: huge balls of blue ice and frozen feces would fall from the sky and smash through house and car roofs. Reportedly, there have been over 30 documented incidents of blue ice hitting the ground since 1979.

Tratong/Shutterstock

The toilets on current airplanes were invented in 1975

And the first one was installed in 1982. They’re called vacuum toilets and when you flush them, a sewer line opens, and the vacuum sucks the contents out super hard until it all ends up in large (leak proof) tanks at the rear of the plane. Wanna see how hard? Watch this video.
 

Airplane toilets are super drought-friendly

The water-saving toilet you use at home that actually doesn’t save any water because you have to flush it four times to get your poop to go down? It uses 1.6 gallons per flush. And those old-school toilets (you know, the one that actually work) use five gallons. Thanks to the vacuum technology, an airplane toilet uses less than half a gallon of fluid. Now you can poop as much as you want on the plane and never worry about wasting water. Except please don’t do that unless you really, really, really, really have to.
 

Airplane toilets can flush upward

‘Cause that’s just how vacuums work. Science!  
 

There’s no way for pilots to dump your dump while in the sky

The tank that holds all of the waste has an exterior latch so there’s no chance a pilot will accidentally empty it into the air while flying over your mortal enemy’s house, as much as you wish they would.

Flickr/Jason Lander

The bathrooms are required by the FAA to have ashtrays

No, you’re not allowed to smoke in there, but in case some moron does decide to light up, the FAA wants to make sure there’s a place for the ashes and cigarette butt to go besides the trashcan, since the trash is all paper products and therefore highly flammable.
 

Your poop and pee is vacuumed out on the ground

You can empty your bowels on the plane, but the plane has to wait until it’s on the ground to do the same. Once it lands, it’s someone’s job (the same badasses who use the glowsticks on the runway) to get in there and suck all of the stuff that’s flushed during the flight. Well, technically a person connects a pump to the plane and then lets a vacuum take it from there, which usually takes around 10 minutes.
 

You can’t get stuck on the toilet if you flush while sitting down

The vacuum is really, really strong, but your butt would have to make a perfect seal on the toilet for you to get stuck. And, of course, Adam Savage tested this out on Mythbusters.

Flickr/David Levinson

You can easily unlock an airplane bathroom door from the outside

Just lift the “lavatory” sign and slide the knob into the unlocked position. But seriously, don’t do this unless there’s a kid stuck inside. Or, you know, your friend is in there.
 

The tap water that comes out of the sink is really, really gross

According an article from the Wall Street Journal in 2002 where reporters tested water on 14 different flights, “almost all of the bacteria levels were tens, sometimes hundreds, of times above US government limits” and included microscopic life like Salmonella, Staphylococcus, and tiny insect eggs (see, larvae!!!). The EPA has since said that there are new guidelines and the water is safe to drink “if you don’t have a suppressed immune system,” but maybe just skip filling your water bottle in the bathroom and order a whiskey instead like a normal person.
 

You definitely don’t want to go the bathroom barefoot or in socks

Is this super obvious? We wish it were, but we’ve seen way too many people pad down the aisle in their socks en route to the toilet. Guess what though? The bathrooms don’t get cleaned while in the air. So that wet spot on the floor? It’s not water; it’s from when some dude was peeing and the plane hit a little turbulence.

Flickr/Sunny Ripert

Still... the bathrooms aren’t the dirtiest part of the plane

No, that honor is held by the tray tables, then the overhead air vents, then the seatbelt buckles, and THEN the bathroom stall locks. In fact, here are the eight parts of the plane you just shouldn't touch.
 

But self-cleaning bathrooms may soon to be a thing

Boeing announced it is researching a prototype that uses ultraviolet light to kill 99.9% of germs in three seconds after every single use.

Jennifer Bui/Thrillist

Four percent of Americans are members of the Mile High Club

According to Cosmopolitan, four percent of Americans say they’ve had sex in an airplane (and probably did it using these tips), but 25 percent of us wish we had. We’re just holding out for those self-cleaning toilets.

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Daisy Barringer is an SF-based writer who is not a member of the Mile High Club, but hasn’t ruled it out. Follow her on Twitter @daisy.

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