Independent testing found dangerous levels of lead in homes and schools, caused by chemicals in the water supply that corroded the pipes.
"So I started building high capacity lead filters just as a charitable effort.
"After Flint hit the news people started taking a closer look at their water and found that lead is a widespread problem in the US," he says.
Replacing pipes can cost millions of dollars which many cities can’t afford.
Mr Roy assesses the type and level of contamination by analysing publicly available data.
Filters cost around $225 (£172), and replacement cartridges, which are needed every six months, cost $65.
Mr Roy has a PhD in chemistry from the University of Maine, and started his first business, a consulting company, while he was still studying.
They’re led by people who study entrepreneurs and that’s a very different thing."
"In the core part of the business you need to be working with people who actually know what they’re talking about."
"I definitely think this will be an eight figure business in five years," says Mr Roy.