Those who love the crispy, slightly chewy crust of Grimaldi's distinctive East Coast pizza have a New York native to thank. Not Joseph Ciolli, the New York-born pizza expert who runs the family chain in Arizona. The secret lies in the large plastic barrels tucked into a cramped room behind the coal-fired oven.

It's the water, which tastes straight out of the Catskills. The result is an authentic New York pizza, each Valley pie tasting as if it came out of an oven in Brooklyn. A sophisticated filtering system scrubs the AZ from every ounce of H2O.

When it emerges from a black hose snaking down from the ceiling, the water may as well have come out of an NYC tap.

"That's the key, I guarantee it," Ciolli said. "It's all about the water."

And for those who doubt water can play such a pivotal part in pizza making, know that the 40-year-old Ciolli earlier this year staked his palate, and the Grimaldi family's century-old reputation, on that very fact.

But more on that later. This story begins in late 2002 in Old Town Scottsdale, just a few months before Ciolli was to open Arizona's first outlet of the venerable New York pizzeria.

Ciolli, who fell in love with the desert while attending Arizona State University, fired a pizza in the Scottsdale restaurant for the first time, using the same exacting recipe that had been in the family since 1905.

And it tasted . . . wrong.

Cheese was perfect; sauce was spot on. But Ciolli's palate, tested over a lifetime of eating Grimaldi's pizza, detected immediately that the dough was off. The texture and taste did not measure up to standards.

Ciolli tried again, making sure ingredients and measurements were perfect (knowing the previous attempt was just as exacting). Again, the crust was flat.

Once he eliminated elevation as a factor (Scottsdale sits about 1,100 feet higher than New York City, so a precise amount of flour was added to compensate), the only variable was water.

A week or two later, Ciolli was in New York on business when he cleaned out a large plastic jug (formerly holding picante sauce) and filled it from the tap. He tucked the jug into his carry-on (prior to Federal Aviation Administration regulations against boarding a plane with so much liquid) and used that water the next day to mix the dough.

The pizza was perfect, confirming Ciolli's suspicions.

New York's water travels hundreds of miles from the mountains to the city, the journey a natural filter. It's unlike Arizona's water, which, as any Valley resident can tell by calcification around faucets, is full of minerals.

Ciolli conferred with a local chemist who, after analyzing the leftover liquid from Ciolli's jug, designed a filtration system that turned Arizona water into New York tap water.

When Grimaldi's Pizzeria opened Feb. 14, 2003, in Scottsdale, New York water flowed like wine (but not into glasses, only into the dough). The filtration has been a part of each of the five Arizona Grimaldi's opened since then, from Peoria to Gilbert.

For the next six years, the proof of New York water's superiority as a pizza-dough ingredient existed with Ciolli's discerning palate. If anyone were to challenge him, Ciolli would defend Big Apple water with every fluid ounce of his being.

And in March, that challenge arrived.

Ciolli, in New York on another business trip, received a call from the Food Network, asking him to be on a three-member panel to test the hypothesis that New York water is what makes New York pizza so great.

The trio would appear on the weekly show "Food Detectives," which explores food myths, to taste three identical pizzas save for one ingredient. One pizza would be baked with Chicago water, another with Los Angeles water and the third with New York's finest.

Ciolli's first reaction to the blind taste-test invitation? "Ah, no, I don't think that's a good idea," Ciolli said. "I could come out looking like a real idiot."

But during the same phone call, he realized he had to live up to his convictions. It was time to trust the palate.

Arriving at the chosen pizzeria, filled with bright lights and cameras, Ciolli wondered what he'd gotten himself into. He had everything to lose and very little to gain. Imagine if he were to pick the pizza made with Chicago water. It would be like the Yankees losing the World Series to the Cubs.

His nerves settled once the pizzas were placed in front of him.

"I could sort of tell right then, just the way the crusts looked," he recalled of pizzas A, B and C. "B just looked like it was made with New York water, just the way it sat on the plate."

As soon as pizzas met palate, Ciolli was sure. He and the other two New York pizza experts chose B as the best, thus the New York, pizza and waited anxiously as host Ted Allen - with all the tension of Oscar night - ripped open the envelope to reveal which pizza was which.

The authentic New York pizza? B.

"I was pretty confident when I picked B," he said. "No, very confident. But it felt great when I heard B. It could've been ugly. A lot was at stake."

Today, filtration workers visit each Grimaldi's restaurant every two weeks to add salt, replace filters and maintain the water system so it keeps pumping out that fresh New York tap water.

And Ciolli has found one more use for his New York water.

"Check out our glasses," he said, holding one up. "See? No scratches. Arizona ice scratches."

The difference was clear.

Details: Grimaldi's has five restaurants Valley-wide. For locations, visit patsygrimaldis.com.