OSAKA -- Drinking water has long been seen as something that comes for free. All you need to do is turn on a tap.

Tsutomu Itaya, owner of the Mirai water shop in Osaka's Kita Ward, serves bottled mineral water to customers.

Despite severe droughts in recent years causing some disruption to water services, Japanese are normally confident that there will always be a ready supply of drinking water.

However, with their palates thirsty for quality water, more people now seem prepared to pay to get something tastier than mere tap water.

The Mirai water shop and cafe in Osaka's Kita Ward, which serves purified water and 17 kinds of bottled mineral water, is cashing in on this emerging trend.

Purified water is served for 100 yen on a "drink as much as you want" basis, while mineral water is purchased by the bottle.

The most popular type -- mineral water from Yakushima Island, located 60 km off the Osumi Peninsula in Kagoshima Prefecture -- costs 150 yen for a 500 ml bottle and 320 yen for a 2 liter bottle. Deep sea water collected off Murotozaki cape in Kochi Prefecture -- ranking second in popularity -- costs 120 yen for small bottles and 200 yen for large ones. Although the cafe also serves coffee and green tea made with purified water for 100 yen per cup, they can be only be ordered after placing a water order.

Tsutomu Itaya, operator of Mirai, said he has tested 165 kinds of mineral water since he started his water shop and cafe business three years ago, but only 17 of them are served at his cafe. The rest simply didn't meet with Itaya's exacting standards.

Of the 17, 16 are from Japan and one is from South Korea's Cheju Island. No water from major beverage companies are sold at the shop.

Although the first year saw very few customers, the number of regular customers began increasing in the second year and sales soared this summer to 1.5 times the level of last summer, he said.

A group of women who work at a nearby office said they come to the shop almost everyday after lunch for a glass of water and a cup of coffee.

"Coffee at other coffee shops is made with tap water and doesn't taste as good as here," said Suzuko Nakano. "The purified water at this shop tastes sweet, which makes the taste of coffee mild and sweet."

Itaya thinks shops that sell and serve quality water will proliferate as people become more health-conscious and sensitive to drinking water for daily use.

"In purifying tap water, we use reverse osmosis membranes, a system developed by NASA," he said. "It is safe, healthy and tasty."

Mirai earns its main income by selling this purified water to some 300 member customers at 300 yen per 10 liters, or 36 yen per liter. It sells 500 to 700 liters a day, Itaya said.

Nobuko Sasaki, 28, from Osaka's Nanba district, comes to the shop twice a week to buy at least 10 liters of purified water.

"Without exception, those who have tried the water say they like it," she said. "Although I have a water purifier at home that makes alkaline ion water, I cannot drink it -- not to mention tap water -- after drinking the water from the Mirai shop."

Before starting his water shop, Itaya worked as a plumber for 22 years. It's still his main job. His long involvement in the business of water, he said, has given him a sense of duty to provide safe and healthy water to as many people as possible.

"Water makes up 70 percent of our bodies," he said. "We should and will be more aware of the quality of water."