Flyers–Why Won’t Airplane Toilets ‘Operate’ Below 16,000 Feet?

Thumbing through Facebook, I saw an interesting post on one of the airplane-aeronautical pages I follow (I am an airplane geek!).

 Is It True Airliner Toilets Won't Work Below 16K feet?

A follower of Aviation Review Materials posted a photo from a very recent flight  they took from Phoenix, AZ to Seattle. It showed a sign on the lavatory door saying  "INOP (inoperable) do not use below 16,000 feet."

The poster wondered why, and we did too.  Looking into it, we discovered something new about airliner technology.  The lavatory toilets depend on old-school physics, apparently.

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The reason? Newer airliner technology 'powers' the toilet by utilizing the air pressure difference between the interior cabin and the thinner outside air at higher altitudes.

This is apparently done to save weight, water, and simplify the process.

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According to the website Satellite Industries:

"Airplane toilets don't work below about 16,000 feet because they rely on a pressure difference between the cabin and outside air, which isn't strong enough at lower altitudes."

So, what do they do in  between sea level and 16K feet?  The planes are equipped with a small vacuum pump, but apparently they fail quite often--hence the sign on the door posted by the Aviation Review Facebook member.

At 16K feet- plus, the pressure difference is enough that the interior pressure of the cabin vs. the outside will create a vacuum that will suck the disposable materials into a sealed tank underneath the cabin in the aircraft. And no, unless there's a leak, airliners do not intentionally dump waste.  There's old wives tales about people nearly being hit by chunks of blue ice from an airliner, but that only happens if there's a leak.

This phenomenon may not seek like a huge deal, but the web is full of posts and stories from travelers who had to deal with inoperable toilets.  Given that  the average cruising altitude of the typical airliner is between 29,000 and 40,000 feet, hopefully the 'vacuum' works for you! SO, if you see this kind of sign, now you know why.