The primary sensing technology that I’ve been using in my health modeling research this year is Hydrosense, a device that consists of a water pressure sensor and some additional hardware for signal acquisition, processing, communication and/or storage. By monitoring water pressure change patterns in a single-family home, Hydrosense lets us identify which water fixtures are in use and help us develop a good sense of which water-based activities are taking place. It’s a cornerstone of our activity and lifestyle recognition efforts.
This technology was conceived and originally designed by Shwetak Patel, Joe Froehlich, Eric Larson and others at the University of Washington.
A few weeks ago, while at the CDC Public Health Informatics Conference, a question was posed to me: “What is the Hydrosense coverage right now considering that not all homes in the US are single-family homes and not all of them are connected to a water supply system?”. I was intrigued by this question and decided to investigate further. Luckily I didn’t have to go very far. Wikipedia and the U.S. Census Bureau had all the numbers I was looking for.
There are 115.9 million homes in the US. About 70 million of these (60.3%) are detached single-family units. Eighty percent of single-family homes are occupied by owners. In terms of water supply, 14.5% of Americans rely on their own water sources, typically wells. Water well pumps are used in this case. The pump sends water to a storage tank with an air bladder that compresses as the water is pumped in. At 40-60psi, the pump stops. When water is used in the home, pressure drops and when it goes below 20psi, the pump starts again.
More than 99% of the US has access to “complete plumbing facilities”, defined as having (1) hot and cold piped water, (2) bathtub or shower, and (3) flush toilet. Homes that lack such water facilities total 670,986, and are usually inhabited by the elderly, the poor and those living in rural areas. Alaska has the highest percentage of households without plumbing.
To sum it up, Hydrosense can be used today in 60% of homes in the US. We would like to enhance it so that it can work reliably in multi-family homes and apartment complexes as well, which will expand Hydrosense’s coverage to virtually every home in the country. Thinking globally, and especially in the context of developing countries, I now wonder how suitable Hydrosense is in other regions of the world.