After a massive water main break, many Boston residents lost clean tap water for up to three days.

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oston-area residents have clean tap water again after a ruptured underground pipe stopped clean water supplies to 2 million people for up to three days. President Obama declared a state of emergency and made federal aid available for affected communities. But how did this happen — and could it happen elsewhere in America? (Watch an AP report about Boston's water leak)

What caused the disruption?
A "catastrophic and unprecedented pipe rupture," according to the Boston Globe. A collar that connected two 10ft water pipes ruptured, but state officials aren't certain what caused the break. Theories include poor construction and installation, or wear and tear. Early suspicions that a minor earthquake was to blame have been ruled out. An investigation has been launched by Governor Deval Patrick.

Where did all the water go?
Millions of gallons flowed into the Charles River. There was no flooding, but sediment washed into the Charles, turning swaths of it muddy brown.

Did the taps stop working?
Not for long. Water was rerouted from disused water mains, but it was polluted with a small amount (3 to 5 percent) of "pond water" from a natural reservoir. As local authorities were unsure what bacteria it might contain, they warned locals not to drink it without boiling it first.

How did the state authorities react?
The Massachusetts Water Resources Authority repaired the pipe in under 48 hours, and state officals distributed approximately 2.5 million gallons of drinking water to affected communities.

How did the people of Boston react? 
Some better than others. Unscrupulous store owners reportedly jacked up prices for bottled water. But more community spirit was in evidence elsewhere — bottling company CPF Co-Op boosted its production levels sixfold to ensure plenty of bottled water was available to the state.

What are the odds of this happening to me?

High, according to one report. The Urban Land Institute said in April that America's urban water infrastructure urgently needs revamping to avert water shortages in the future. It named 14 cities — including Boston – with particular problems. "Regional and local problems with both water quantity and quality will continue without a broad-based cutback in public water consumption and a change in how and where we build," said a spokesperson.

Sources: Boston Globe, Boston Herald, Urban Land Institute