RoyalFlush: non-invasive water level monitor to prevent toilet overflows

Farshid Salemi Parizi, Josh Fromm, Shantanu Deshpande, Shwetak Patel


Neglected toilet overflow can cost thousands of dollars through mold growth and damage to furniture, upholstery, electronics, and household appliances. We propose RoyalFlush: a novel non-invasive overflow system meant to detect such events in their early stages and prevent them from escalating. RoyalFlush uses a floating capacitive sensing technique that relies on the sizable difference between the dielectric constants of water and air for tracking changes in the water level. Capacitive sensing in this way does not require any hardware inside the toilet bowl. RoyalFlush consumes only 150 μW of continuous power, allowing it to operate for a couple of years on a 9 volt 625 mAh alkaline battery. We evaluate RoyalFlush on 10 different toilets in a controlled 60-minute experiment to validate its functionality. Additionally, we deployed RoyalFlush into 5 homes for 24 hours to test in real-world scenarios. During the real-world deployment, RoyalFlush identified overflow events with a precision of 98.16% and a recall of 100%.