Millions of gallons of water rushing through neighborhoods and flooding homes. It's a situation that's happened in the past and likely could happen again if crews don't repair a failing pipeline.
According to Tucson Water, a section of pipeline on the west side along San Marcos Boulevard between Greasewood and Mission Roads is showing signs of weakness.
To prevent a major break, crews will shut down the pipeline Tuesday to begin repairs.
In February 1999, 60 million gallons of water flooded a west side neighborhood after a 60-inch pipe burst.
"It was catastrophic for the neighbors that lived downhill because it literally flooded the neighborhood," said Tucson Water spokesman Fernando Molina. "Caused a lot of damage to many homes."
After that incident, Tucson Water installed a $5 million acoustic monitoring system into major pipelines that can sense when wires wrapped around the pipes are breaking.
They recently noticed a lot of breaks in that section of pipe along San Marcos Boulevard. That could be a sign that the pipe will burst.
Not only would that mean flooding in the neighborhoods surrounding the pipe, but about 70 percent of the city would lose water service.
"We've made a decision to avert any kind of disaster, disastrous break like we had in 1999, we'll be shutting down the pipeline tomorrow, converting to groundwater system so that we can keep delivering water to our customers," said Molina.
The groundwater system is Tucson Water's backup plan. Usually, water comes from the Clearwater Facilities in Avra Valley and is renewable Colorado River water.
When they make the switch to groundwater, customers all over the city might notice their water looking white or milky when they turn on the faucet.
"It clears up," said Molina. "It will clear up from the bottom to the top. It's just natural. It's just air that's in the water at that point."
He says the water is still completely safe.
Some customers may notice a temporary drop in pressure during the switch, but overall the repairs shouldn't cause any disruption in service.
Tucson Water expects to finish repairs and switch back to their renewable Colorado River water by the end of May.
