A major pipe bringing water to the Boston area has sprung a "catastrophic" leak and is dumping eight million gallons of water per hour into the Charles River. Governor Deval Patrick declared a state of emergency and issued a "boil-water" order for Boston and dozens of other communities."The water is not suitable for drinking. ... All residents in impacted communities should boil drinking water before consuming it," he said at a news conference this afternoon.Patrick said the state had asked bottled water companies to make more water available in the state and emergency drinking water supplies could also be made available to the affected communities through the National Guard."I ask everyone to check in on elderly or vulnerable neighbors," he said, and he asked people to avoid "unnecessary use of water, such as washing cars and lawnwatering."The break is in a 10-foot-diameter pipe on Recreation Road in Weston, the authority said in a statement."That is a catastrophic break and we are currently activating the reserves," said MWRA spokeswoman Ria Convery. MWRA officials said just over a million people would be affected in 31 cities and towns.People flocked to stores to buy bottled water when they hear the news. In Lexington, an hourlong run on water cleared a supermarket's shelves. In Boston, restaurateurs declared the boil order a major inconvenience and police planned to fan out with bullhorns to some neighborhoods to notify people of the order.The failed tunnel connects the MetroWest Tunnel to the much older City Tunnel, as water flows east through the suburbs from reservoirs in central Massachusetts towards Boston, officials said.MWRA Executive Director Fred Laskey said the leak began between 10 a.m. and 11 a.m. today and the pipe continued to break until it failed "catastrophically."The "good news" is that "we continue to maintain the flow for firefighting" and for toilets and other non-drinking purposes, said Laskey, who joined Patrick at a news conference at the Massachusetts Emergency Management Agency headquarters in Framingham.Because of turbidity it is impossible to see down to the leak and contractors and engineers have to wait until the tunnel drains – hopefully by tomorrow – until they can figure out what went wrong, Laskey said.In a case of what a grim Laskey called “Murphy’s Law”, a system that would have protected against this catastrophic failure is under construction.A far older aqueduct built in the 1940s – the Hultman - that carried water on the last leg of its journey to Greater Boston – was so riddled with leaks MWRA officials built the MetroWest Tunnel seven years ago. The Hultman was then shut off to repair the leaks and a series of connector pipes were built – much like the one that failed – to ensure clean water gets to the City Tunnel and then to faucets. Now, Laskey said, "we thought we could rely on this connector during that rehabilitation. It is Murphy’s Law."The City Tunnel carries an average of nearly 179 million gallons per day towards the city, officials said.Convery, the MWRA spokeswoman, said that a backup system would be used, which would pull water from the Chestnut Hill Reservoir and Spot Pond Reservoir, as well as an alternate aqueduct, the Sudbury Aqueduct.But she said the water that flows from the system would need to be boiled. Communities as far north as Wilmington and as far south as Stoughton would be affected.Water gushed out from the ground at the MWRA facility on Recreation Road near Interstate 95 in Weston this afternoon and flowed rapidly downhill into the Charles River. Crews stood by, waiting for the water to be shut off, as a crowd of reporters watched.Laskey said he could not speculate how long the leak would take to fix. However, if a temporary patch to the steel pipe does not work, a new custom-made piece of pipe may have to be created.“I don’t really want to speculate,’’ Laskey said at the scene in a phone interview. “We gotta get there to know.”The state Department of Conservation and Recreation said the millions of gallons pouring into the Charles would not be a problem, even as the river’s elevation has risen.“Our dams can handle this,’’ said spokeswoman Wendy Fox.Tom Lindberg, an MWRA spokesman, said no homes or properties in the immediate area were affected by the rushing water.The MWRA system provides water to a total 48 communities, according to the authority's website. The water comes from the Quabbin Reservoir, 65 miles west of Boston, and the Wachusett Reservoir, 35 miles west of Boston, and flows through aqueducts east into the Boston area.