“Some private jets have a shower on board.”
Verdict: Yes, and not just the converted airliners. A shower is an option on the Gulfstream G650ER, G700 and G800, the Bombardier Global 7500/8000 and the Falcon 8X/10X, typically in the aft lavatory. On Boeing and Airbus business jets, showers have been standard luxury for decades, and the Sultan of Brunei's 747 has full bathrooms. The catch is water: business-jet showers carry enough for a few minutes each, and every gallon is weight.
Water on an aircraft is a compromise. A Global 7500 shower system holds roughly 30–40 gallons, enough for two or three short showers on a 14-hour flight, and the tank, pump, heater and drain add around 200–300 lb. Gulfstream has offered a shower in the G650ER's aft lavatory since around 2015, and made it a feature of the G700's grand suite. Dassault's Falcon 8X shower option launched in 2017.
On larger cabins the engineering is easier: a Boeing BBJ or Airbus ACJ can devote a full room to a bathroom with a proper shower and a mirror wall, and Lufthansa Technik and Jet Aviation have built dozens. The Emir of Qatar's aircraft and Air Drake are well-documented examples.
The fun detail is the pressure. Cabin-pressure differentials and the need to drain water safely mean business-jet showers have low-flow heads and a timer; some owners describe them as adequate rather than luxurious. Nobody is soaking in a bath at 45,000 ft — bathtubs have been proposed and rejected on weight and slosh grounds for decades, though one Airbus concept famously included one.
So: true, useful on the longest flights, and less common than the brochures suggest because most buyers prefer the extra seats.
Sources: gulfstream.com · bombardier.com · dassaultfalcon.com
