RIVERSIDE - The regional agency that delivers water to 2,500 homes and businesses in western Murrieta is preparing to change the way it treats those customers' drinking and bathing water, officials said Wednesday.

That change is expected to affect the daily lives of kidney dialysis patients and people with fish tanks in their homes, said Joe Bernosky, engineering manager for the Riverside-based Western Municipal Water District. But for just about everyone else, including those with swimming pools, the switch should not require any changes in lifestyle.

Western board members discussed the plan in a work session Wednesday. The plan is to discontinue using chlorine to disinfect water delivered to the older section of the city west of Interstate 15, between Elm Street and the northern city limit, and to switch by summer to chloramines, compounds composed of chlorine and ammonia.

The district board is scheduled to consider on Sept. 19 spending about $200,000 to design the new treatment system, which will disinfect water pumped from three wells. The wells and the service area were acquired by the district in November 2005, when it took over the former Murrieta County Water District.

"What this is going to do is give us more flexibility in our operations," Bernosky said. "This will allow us to take a well down for maintenance a lot more easily."

Bernosky said the district would like from time to time to pull in imported river water from the nearby Lake Skinner treatment plant to serve the westside Murrieta residents.

Under existing conditions, the proposal is problematic because the river water is disinfected with chloramines and the westside well water is disinfected with chlorine. As a result, district officials said, blending the two sources could compromise the quality of water being piped into homes.

On the other hand, the change could create problems for people whose kidney dialysis machines are not set up to filter out chloramines, and patients should prepare to make adjustments, officials said.

At the same time, fish tank owners should prepare to add tablets designed to remove chloramines, which are harmful to both saltwater and freshwater fish, officials said.

"It's available in any pet store," Bernosky said.

Customers in other parts of Murrieta, served by three other agencies, already receive water that has been disinfected with chloramines.

Western serves water directly to 24,000 customers in Murrieta and Riverside. It also delivers imported water to other agencies in a 527-square-mile territory straddling the Interstate 15 corridor that has a population of 826,000 people.

- Contact staff writer Dave Downey at (951) 676-4315, Ext. 2623, or ddowney@californian.com.