<HTML>I'm sure the short tank installation allows for more breathing space for the humidifier, but a standard upright tank will also barely fit. I've used short tanks for several installs including one yesterday, but it holds considerably less water that the standard tank. It requires far more watering and the grace period before the tank runs dry after the light flashes is an issue. I usually keep an upright and a grand short tank system in stock and bring it along with a standard system if I have a question about fitting. Good luck. Bob Russell</HTML>