That maturity can be found at Donnelly's, a 30-year-old PHC company located in Philadelphia. Owner Marty Donnelly became a diversification disciple during the recession of the early-1990s. He joined Contractors 2000 and decided to dip into another business: air conditioning.

After reading up on water quality issues and tracking the rising stocks of U.S. Filter, Culligan and some European companies, Donnelly decided to diversify into the home water treatment market. "I could see the equipment and the level of install, and I knew we could do better," he says.

Donnelly began selling unbranded products, but soon learned that he needed to differentiate his company from the competition. He searched out water treatment equipment manufacturers that would give Donnelly's a unique presence in its market.

He joined the WQA and got the training bug. He hired trainers from the water industry to teach his employees the basics of water. Every month Donnelly brings in a trainer from a manufacturer; he also sends employees to manufacturers' sites to learn. "We knew we had to talk the talk," he explains. "And through education, testing and certification, we do."

Donnelly technicians are not only involved in service work, they are also involved in opportunity selling. The technicians are in customers' homes and can see what kind of damage hard water can do to water equipment. "We can repair or replace the equipment, but we haven't solved the problem," he explains.

About 85 percent of the United States population receives its water from community water systems. "City water is general purpose," Donnelly says. "We believe in a 'whole house' water system, where we are cleaning the water and providing higher-quality water to equipment and appliances."

And the public wants high-quality water, Donnelly says; just look at how much shelf space is dedicated to bottled water. In most stores, bottled water takes up a complete aisle.

And others are getting in on the water quality bandwagon.

"There are water municipalities that are offering point-of-use water softeners to its customers," he says. "Why don't we as plumbing contractors provide this service to our customers?"

Home water treatment is a growing industry and is a tremendous opportunity for today's plumbers. But they need product and industry training, as well as knowing the local water issues, to succeed.

And they need to realize the value of the services and equipment they are offering. This shouldn't be business at the cheapest price, Donnelly says.

"The professional entrepreneur in the water business knows that it is his only business, and he knows how to keep his customers satisfied," he says. "It's a hard lesson to learn, but an important one."