Sometimes while making small improvements to a product, people get an idea that leads to something very different. That’s what happened with David Malcolm.

Mr. Malcolm took over the family business, making sprinkler systems, in 1992. He continued a project his father had been working on just before he died: finding a new use for a low-flow sprinkler designed for farms. Mr. Malcolm decided to install the sprinklers on golf courses and then added an innovation of his own—a sprinkler-type nozzle that could fit on a hose and would enable golf courses to touch up dry patches without turning on the whole system.

Then inspiration struck again. “I was demonstrating the hose nozzle at a golf course and I suddenly thought to myself that this would make an incredible shower head…and then I thought it was perfect timing because water and energy conservation had become hugely popular in the U.S., and there was an extreme drought happening in California,” he says.

That was nine years ago. It took Mr. Malcolm close to two years to complete what he calls “a difficult transition” to shower heads. Unlike golf-green nozzles, Mr. Malcolm says, shower heads have to work consistently over a much wider range of water pressures and water temperatures.

Today, Mr. Malcolm manages a team of seven from his company’s headquarters in the small Northern California mountain town of Coarsegold, and the company focuses entirely on shower heads, mostly selling to universities, prisons and other institutions. Revenue is close to $1 million, Mr. Malcolm says.