MURRIETA -- Randy Sonderhouse says he knows how easy it is to waste time -- and water -- in the shower. After his wife noticed he was taking unusually long showers, the Murrieta resident decided to invent a solution.

That solution, a water-proof alarm timer Sonderhouse designed, the Shower Professor, is now for sale for $10. It can be ordered from his Web site, http://showerprofessor.com.

Sonderhouse said the device has helped him reduce his shower time from 15 or 20 minutes down to just 5 minutes. That saves about 25 gallons of water per day, he estimates, as well as the energy used to heat the water.

"The device changes behavior because your time is right in front of you," Sonderhouse said.

The Shower Professor is made to be simple, Sonderhouse said. It has a digital screen and four buttons. Three buttons are for shower times: 5 minutes, 7 minutes, and 10 minutes. The fourth gives you an extra minute.

Five seconds before the time is up, the alarm goes off -- audible but not annoying, Sonderhouse said.

Five Percent, an environmental blog, favorably reviewed the device in a comparison with other shower timers, praising the legibility of its display, low price and ease of use.

Sonderhouse said he designed the device himself, with the assistance of engineers. For the manufacturing, he contracted with a company in China, which recently sent him 5,000 of the devices.

"I had to make the tools to run a production line," Sonderhouse said of his dealings with the company, which he said he found online. "Then I had to commit to buying so many, or they won't even do it for you."

Sonderhouse said he gradually firmed up the details of the Shower Professor as the design process continued.

"I sent them a picture, I told them what I wanted it to do," Sonderhouse said. "We went through about four different prototypes. We went through about six months of work to get it done. I started back in May."

In addition to selling through his own Web site, Sonderhouse said he's sold units through eBay. In 10 days, he said, he's sold 16 devices, in 10 states and Canada.

"I had a mom in Florida with three daughters who wrote me. She said, 'This device is going to solve our time management, our water conservation problem, thank you so much for creating it.' I shipped it out this morning," she said.

Contact staff writer Bradley J. Fikes at (760) 739-6641 or bfikes@nctimes.com.