The drinking water disinfectant for the upper Kula water system will return to chloramines around March 15, the Department of Water Supply said Friday.

The department temporarily switched to chlorine in October as part of maintenance on the 8-million gallon reservoir at the Olinda Treatment Facility, which serves upper Kula and was on reduced service.

Upper Kula customers currently are getting water from the Piiholo Water Treatment Plant in Lower Kula, which uses direct filtration and chlorine, the department said.

The Olinda plant has used microfiltration technology and chloramines (chlorine and ammonia bonded together) since 1985. The water department uses chloramines in the upper Kula system because of higher organic matter occurring naturally in the water from the higher elevation Waikamoi rainforest, a water department spokesperson said.

The organic matter combines with chlorine to create trihalomethanes, a suspected carcinogen. Use of chloramines has been shown to deliver the lowest levels of trihalomethanes, whose levels are regulated by state and federal agencies, the water department website said.

The switch to chlorine helps reduce bacterial growth, particularly at the end of waterlines or in homes. Many utilities throughout the country using chloramines as a system disinfectant routinely convert to chlorine to hinder bacterial growth in their systems, the water department said.

The only change customers will notice is a reduced chlorine odor or taste, the department said.

For kidney dialysis patients, chloramines, as well as chlorine, need to be removed from water used in the process. Chloramines in the water would be toxic. Dialysis patients should contact their medical professional for more information.

Chloramines are toxic to fish and must be removed from tank water, just as chlorine is. Although chlorine rapidly disappears from aquarium water on its own, that is not the case with chloramines; steps should be taken to remove the chemical. Most pet stores sell dechlorinating agents. Chemicals used to remove chlorine should work just as well for chloramines.

For questions about water quality, call the water department laboratory at 270-7550 or log on to www.mauiwater .org. For health concerns, call the Maui District Office of the state Department of Health at 984-8200.