Lisa Lehnertz, 51, battles liver illness. So, in 1994, when the water in her Isthmus-area apartment started appearing discolored and speckled with the small, black flakes that are the telltale signs of manganese, she took notice.

Lehnertz bought a pitcher with a filter on it for drinking water. Mostly, though, she drinks bottled water.

Lehnertz is not alone.

Many people in Madison, especially on the East Side where water has been discolored for some time, now either drink bottled water or use water filters in their homes.

But Lehnertz would rather be drinking tap water.

"I really think it's sad you have to go to this extent," Lehnertz said. "I've been here all my life and I've never seen anything like this."

Madison and Dane County public health officials recommend against anyone with liver problems drinking water contaminated with manganese. A health advisory warns that people with liver disease may have trouble flushing the mineral from their bodies and too much manganese can cause neurological problems.

Madison's water problems have been a boon to businesses that market and sell water filters and bottled water.

Carl Nurmi, a territory manager in Madison for Culligan, said sales of both water and filters started taking off five or six years ago.

"People want to see clean water," Nurmi said. "They don't want to see brown water. They don't want to see black flecks."

To get rid of manganese - perhaps the most pressing water problem facing Madison residents - it's best to buy an oxidizing filter, said Glen Schlueter, an environmental engineer with the state Department of Commerce Safety and Buildings Division.

Oxidizing filters use chlorine or bromide to turn the manganese into a solid. A filter then catches the manganese particles, removing them from the home's water supply.

Such filters are generally installed near where water enters the home, said Schlueter, whose job is to provide consumers with information about water filters.

The filters are expensive, Schlueter said, with the least expensive probably selling for about $800. But Schlueter suggested also talking to filter retailers about the possibility of leasing.

If you are concerned about volatile organic compounds, or industrial chemicals such as cleaners and solvents, Schlueter said granular activated carbon filters are the way to go.

They are similar in price to oxidizing filters, said Schlueter, starting at around $800.

Unfortunately, Schlueter added, the filters such as the one used by Lehnertz on her pitcher do little to get rid of manganese. Pitcher filters do work for reducing the taste and odor of chlorine and for removing lead and copper.

The pitcher filters, such as those manufactured by Brita, are available at most large retail stores and are priced from around $20, according to Schlueter.

Homeowners have to purchase filters for the particular problem they are trying to solve. No filter works for everything, Schlueter said.

With the exception of pitcher-style filters, Schlueter said, the state requires that retailers sell only filters that are certified by the state and accompanied by a letter that indicates the state's approval of the device. Consumers should always ask for the letter of state approval, Schlueter said.

It's important to comparison shop, Schlueter said, adding that prices for filters can vary greatly and a homeowner could end up spending as much as $3,000 or more for a top-of-the- line system.

Shoppers for home filters can go to either a larger retailer such as Home Depot or a more specialized plumbing business, such as Hellenbrand or Culligan, Schlueter said. If you have specific questions, a store that specializes in treatment systems and is a member of the Water Quality Association, a trade group, is best, he added.

As for bottled water, a report by Consumer Reports in August 2000 pointed out that it isn't necessarily safer than tap water because it is frequently tap water that has been processed and repackaged.

But an analysis of major bottled water brands by the consumer watchdog organization revealed few worrisome results.

Tests showed bottled water meets EPA standards for contaminants such as arsenic and industrial chemicals.

Bottled water is regulated by the Food and Drug Administration, whose standards for contaminants take into account the EPA's tap water standards.

Boiling water will kill bacteria but won't remove manganese or chemicals.