[retiredguy123]

Originally Posted by ton80

They are trying to flush the water lines through the hydrants not flushing the hydrants only. Some systems use higher Chlorine residuals treating to disinfect the water lines.

See below an article published in 2024:

Sumter County gathers important information while flushing fire hydrants
by Staff Report
January 28, 2024
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Sumter County has been conducting a fire hydrant flushing program that will soon begin in Wildwood.

The purpose of this annual program is to ensure fire hydrants are operational and in good working order. Regular testing helps identify potential issues, such as low water pressure or obstructed valves, allowing for prompt maintenance and repairs.

During the testing process, location data is collected to add to the hydrant layer on the Sumter County GIS interactive map. This data not only helps the fire departments, but the public can access this information via the Sumter County website (Sumter County, FL - Official Website | Official Website). Municipalities also use the water data to simulate high-flow conditions to determine pressure and flow-producing capabilities of the water distribution system and for calibration of hydraulic models.

In addition, the data is used to assist the insurance industry with the necessary data analytics as the Insurance Services Office (ISO) collects, maintains, and analyzes a vast amount of water system information from the 45,521 fire protection areas evaluated throughout the country. It’s part of the nationally recognized fire protection rating program, Public Protection Classification (PPC), and one of the first lines of defense for residential fires are water systems with fire hydrants. The PPC program surveys communities, obtains data, analyzes the data, and then provides information to communities and insurers. The result is better preparation for firefighting budgets, capital improvements, system/hydrant maintenance, the ISO evaluation and fire department training.

Annual inspections of the Center Hill, Webster, Bushnell, and Lake Panasoffkee hydrants were completed; therefore, the hydrants in Coleman are currently being flushed and then the contractor will begin working in Wildwood.

There will be no interruption of service while this is in progress.

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The OP's question was about how long it takes. The article you posted is from 18 months ago and doesn't say anything about how long you need to leave the hydrants open. 1.5 hours seems like a lot of water to waste, especially if they are opening every hydrant.