Nick Knoll’s running-toilet alarm uses a magnetic switch and a floating magnet in the toilet tank to signal when the tank has filled. A metal bracket holds in place a plastic tube that serves as a guide for a foam float with an attached ring magnet. A magnetic switch within the tube applies power to a timer circuit until the toilet tank fills. The timer circuit sounds an external alarm intermittently when the tank fails to fill within 45 seconds. A basic NE555 timer integrated circuit and four passive components create the timer circuit. This alarm should get an apartment dweller’s attention so he or she can jiggle the toilet handle and correct the problem. And they can call Nick, too, if the problem becomes a nuisance.