ST. PETERSBURG — It's the water.

It has been the mantra of New York City pizzerias and bagel bakeries for decades. It is why my overhead compartment smells strongly of garlic and onion on flights south from LaGuardia or JFK; it is why Totonno's in Coney Island, Patsy's Pizzeria in East Harlem and John's in the West Village are always overrun with supplicants. It is one of the many reasons New Yorkers can be annoyingly smug.

I suppose I've drunk the Kool-Aid (a beverage that is, after all, 90 percent water with a soupcon of dextrose, citric acid and food coloring). But on Friday, a St. Petersburg pizzeria put it to the test: One pizza made with St. Petersburg water, one with water that had been engineered to closely approximate that of the Bronx, each pizza identical in shape and size and ingredients. Top Slice, a mostly takeout pizzeria that opened downtown at 21 Third St. N in June, would prove it, once and for all and unequivocally: New York water is elemental when it comes to good pizza.

I was the taster. I tasted them blind, not knowing which was which. I had strong opinions.

But first, some science. New York City is the nation's largest municipal water supplier, 90 percent of which comes from the Catskill/Delaware watershed about 125 miles north of New York City. The water passes through the world's largest ultraviolet disinfection facility in Westchester County, is treated with chlorine, phosphoric acid and sodium hydroxide to disinfect it and raise the pH level to around 7.2 (a pH of 7.0 is considered pure water).

If you ask Gary Lane, vice president of sales for New York Watermaker, what makes New York water New York water is the unique composition of total dissolved solids, calcium and magnesium in very specific proportions, plus that neutral pH. These chemicals help activate the glutens in flours without making them too tough or too weak.

Getting the water to Florida started with a known ritual. Paul Errigo, who worked at water filtration company Green Crown Water in New Jersey, was bringing bagels down to his family in Florida.

"Why are you doing that?" asked his colleague and engineer, Emmanual Moya.

"Florida bagels are terrible. It's the water," replied Errigo.

"Um, we could fix that," said Moya.

Errigo and Moya debuted New York Watermaker at the International Pizza Expo in Las Vegas in March. The machine strips out chemicals and inserts those that mimic the water of any city.

Top Slice owners Shan Bakrac and his uncle Benny Broqui heard about it. With pizzerias in New York and Orlando, they were having a dickens of a time getting the dough right in St. Pete. Too gummy, too sticky, too cracker-like and crunchy. It required too much yeast, too high a baking temperature. The problem, they determined: St. Petersburg water. They bought a machine.

Top Slice in St. Petersburg is the first restaurant in Florida to install the New York Watermaker system, a big gray box above the soda fountain that works silently to give this colorless, transparent, odorless, tasteless liquid a New York accent. It's a 10-year licensing agreement, a total commitment of $45,700 that breaks down to $12.50 per day.

They are not the first bakers in the area to develop a workaround. For the past 18 years, Mike Sarmat at Eddie & Sam's in downtown Tampa purportedly brings in trucks full of three pallets of New York water every three months (it's Catskills water, technically). That's 36 cases, six gallons in a case, costing them about $12 per gallon when you factor in shipping. 18 Bagels Co. in South Tampa (which used to be called Nosh, the Original Brooklyn Water Bagel Co. before that) has a water filtration system that approximates New York water.

A lot of do-re-mi for H2O. Is it worth it?

I tried the water by itself: The New York-clone water was neutral, refreshing, very little flavor on the finish. The St. Petersburg water was more eau du garden hose.

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They set down two crusts before me, no sauce, no cheese, no nothing. One was pale and pocky, bubbles quickly turning cracker-brittle, the interior a little doughy. The other crust was a darker golden color with a good chew, its flavor somehow richer and more balanced. Exhibit A: St. Pete. Exhibit B: NYC.

A while later, two finished cheese pizzas, identical sauce, identical cheese. The one on the left reminded me of all the times I'd ordered a walking slice in New York: Paper plate underneath to catch the drips, you fold it down the center to make a long, skinny triangle, the point tender and drooping under the weight of cheese, the puffy cornicione something you nibble to cut the cheese's richness, a little grease inching down your wrist and considering an incursion on your elbow if you're too preoccupied. A New York pie.

There's the scene in The Miracle Worker when Anne Sullivan looks on as Helen Keller runs her fingers under the tap. This was not dramatic like that. But still, it's the water.

Contact Laura Reiley at lreiley@tampabay.com or (727) 892-2293. Follow @lreiley.