CHICAGO (CBS) — Mayor Rahm Emanuel is reiterating his support for the city’s campaign asking homeowners to voluntarily install water meters.

As WBBM Newsradio’s Bob Conway reports, City Hall wants homeowners to get the meters put in so it can start charging them based on the amount of water they use rather than an estimate.

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The Chicago Tribune reports only about 20,000 property owners have volunteered for meter installation the last two years, but the mayor says he is not ready to make them mandatory.

The Chicago Department of Water Management tells the newspaper it hopes to have 45,000 of the free meters installed over the next three years. The department expects the number of meters will increase in the next few years as homeowners see they’ll save money by getting a meter installed.

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Water rates will double by 2015 to pay for improvements to the city’s sewer and water pipes, but metered homes will see bills rise less.

Those with a water meter will see a hike from $339 last year to $694 in 2015, compared with a hike from $450 to $920 for those without meters, the newspaper reported.

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LISTEN: WBBM Newsradio’s Bob Conway reports