Maui Discussion

Ask the Mayor: Why Does the County Drain Hydrants and Standpipes?

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Water repairs. Graphics: Maui Now.

Department of Water Supply technicians conduct hydrant and standpipe flushing for water quality purposes. Graphics: Maui Now.

Department of Water Supply technicians conduct the flushing for water quality purposes

Mayor Alan Arakawa answers some of the most-asked questions submitted to his office staff.

Hi Mayor:


Q: I live on Omaopio Road and every so often I see a county truck at the yellow water pipes “draining” water. It has got to be hundreds (if not thousands) of gallons of water pouring down the road. What is the purpose for this? Can this water be used in other ways? It just seems very wasteful. Thank you for clearing this up. Aloha.

A: Regulated flushing helps prevent water from stagnating in dead-end locations by scouring the inside of the pipe, removing sediments, including built-up silt and biofilms, maintaining chlorine residuals, and clearing the system of any discolored water.

Department of Water Supply technicians conduct the flushing for water quality purposes, but the amount of water that is flushed is different for each site depending on the location of the hydrant/standpipe in relation to the main line. Calculations were done to determine the flushing time needed to move the water from the main line to each hydrant/standpipe.


Unfortunately, it would be extremely costly and impractical to collect the flushed water in a tanker, which would require a tanker truck, driver, flag-man and technician; this represents three vehicles, three employees and numerous additional work hours to flush one hydrant. The water also cannot be flushed onto an adjacent property due to the speed of the flowing water, which could damage landscaping or create other problems.

Want to Ask the Mayor?

Submit your questions about County of Maui programs, services, operations or policies to Mayor Alan Arakawa via email at [email protected], by phone at 270-7855 or by mail to 200 S. High St., 9th Floor, Wailuku, HI 96793. Questions submitted will be considered for inclusion in the Ask the Mayor column.

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