Fluidmaster would like the opportunity provide help. Here is a tip that may solve your problem, when the handle falls off that means the arm on the inside of the tank is not inserted all the way through the mounting base. Simply remove the mounting base from the tank and remove the optional spacer, then reset the mounting base and push the arm until it snaps into place. The handle should stay on from this point. Visit our website Fluidmaster.com/support for videos, troubleshooting tips, email, chat with a technician or call toll free 800-631-2011. We are available Mon-Fri from 5:30 am – 5:00 pm PST