Three times this year, water and sewer pipes have burst across Miami-Dade County, flooding streets and houses, tainting bay waters and disrupting lives.

In March, a 54-inch water main break flooded homes in Hialeah and left a massive sinkhole. Nine days ago in Northwest Dade, a 72-inch sewage pipe burst and gushed raw sewage into Biscayne Bay. Last week in Miami Lakes, a county bus got stuck in a sinkhole from a broken 12-inch sewer pipe.

In a county filled with aging pipes and not enough money to repair them, those mini-disasters may be just the start.

Miami-Dade's records document $325 million in pipe repairs needed in the next 10 years -- repairs that, for now, remain unfunded. A proposal to hike water and sewer fees by 18 percent, mainly to bankroll upgrades, was shot down last year by county commissioners leery of sticking taxpayers with such a steep hike.

One fallout: The Water and Sewer Department lists its top challenge as aging infrastructure. Much of it is more than 40 years old.

"Think of our infrastructure as your house,'' said Peter Velar, the department's assistant director of budget and capital planning. "Right now we have an aging house and we got to go out there and try to replace and upgrade our system as much as possible just to meet the normal operations of the house.''

Not paying the plumber's bill can have serious consequences.

The county's buried maze of water pipes -- stretching 7,500 miles -- pump water to kitchens and showers. Another 6,100 miles of pipes take away waste. A break can create not only mayhem, but pose health risks.

Old pipes are a problem across the country. Each year 240,000 water mains break in the United States and that number is on the rise, according to the U.S. Environmental Protection Agency.

"We've allowed our safety margin to degrade,'' said D. Wayne Klotz, a civil engineer and former president of the American Society of Civil Engineers. "You have greater demands put on old infrastructure that's past its useful life. And that's a recipe for disaster."

In Florida, drinking water ranks among the state's top three infrastructure concerns, according to the American Society of Civil Engineers. The group estimated Florida needs to invest more than $15 billion over the next two decades to address the problems.

In Miami-Dade County, WASD each year replaces about 25 miles of water pipe, less than half a percent of its system. Experts recommend replacing 1 to 2 percent a year.

"This is a national concern of aging infrastructure,'' said Jennifer Messemer, WASD spokeswoman.

To upgrade or replace old water pipes, the county will spend $38 million this budget year. Sewer upgrades will get $48 million. For the next five years, the department has budgeted about $25 million a year for each ``renewal'' fund for water and wastewater.

Yet for years, repairs have been delayed, "resulting in expensive equipment failures in the form of water and sewer main breaks, plant failures and decreased efficiency of operation,'' the WASD's business plan states.

HIALEAH FLOOD

When a 54-inch water main burst in Hialeah in March, the gushing waters awoke residents in the middle of the night.

Dozens of homes suffered water damage, forcing families out. Power was cut at about 100 homes as a precaution. And the rupture left a huge sinkhole -- 10 feet deep and 40 feet wide -- that derailed traffic on West Fourth Place, or Red Road. It cost more than $600,00 to fix.

It was the second time in a decade the pipe, at least 40 years old, had burst. The cause: age.

It's still not known what caused a 72-inch sewage pipe on Northwest 18th Avenue and 157th Street to burst June 18. Many factors can contribute, including materials and maintenance.

The break spilled 20 million gallons of raw sewage into Biscayne Bay, closing some beaches and contaminating waters. Afterward, tests of bay water found elevated levels of fecal coliform, a bacteria.

Dr. Gordon Dickinson, chief of infectious diseases at the University of Miami Miller School of Medicine and Miami VA Hospital, said it is a major concern if sewage spreads into swimming waters.

"You don't drink the water when you swim. But you might get it in your eyes, nose and mouth,'' Dickinson said.

A burst in a smaller pipe in Miami Lakes -- a 12-inch sewer force main -- spilled 1,000 gallons of sewage this past week. The cause was not immediately known. The repairs: $10,000.

But the spill caused a headache in the neighborhood, and a county bus with a dozen passengers got stuck in a sinkhole.

``Within minutes it smelled like rotten eggs,'' said Rita K. Aguiar, who manages a gas station next to the break in Miami Lakes.

That smelly sewage can carry parasites, viruses and bacteria such as E. coli.

"The risk of illness depends on the type and the duration of exposure to the sewage,'' said Lillian Rivera, administrator for the Miami-Dade County Health Department.

Rivera urged residents to follow safety measures, like washing their hands, if they come into contact with sewage and heed health advisories.

She said if a water main break compromises the quality of drinking water, health officials tell residents to boil water or use bottled water.

"We take water very seriously,'' Rivera said.

Meanwhile, WASD crews go looking for leaky water pipes and listen to recorded noises for the tell-tale hissing sound. The wastewater system has its own preventive program: TV cameras check sewer lines heading to pump stations for cracks and a database keeps tabs on force lines. Problems are prioritized.

RAISING RATES

To pay the full bill just for old water pipes, the county would have to raise water rates by 20 to 25 percent, said Velar. It would need more for wastewater.

Last year he didn't get the 18 percent rate hike he requested. Instead, the county approved a 6 percent rate increase in October and another 6 percent increase in April. That boosted the average monthly bill to $40.03 from $35.74 last year.

"We understood the position the board was in,'' Velar said, noting the tough economy. "We therefore said we would be able to live with this alternative, reminding them all it did was postpone greater rate increases into the future.''

WASD still has one of the lowest rates for a utility its size, according to a comparison on the department's website. It shows its average bill to residents is lower than what peers in Florida, like Palm Beach County and Cape Coral, charge.

Jacksonville's former water director Allan Williams said it can be difficult for utility managers to win approval for rate changes from governing boards facing public pushback.

"People don't want to pay for this so they take it for granted,'' said Williams, now the head of the water department in Greensboro, N.C.

But by keeping rates artificially low, he said "the effects are going to snowball and it's going to become a disaster.''