USA TODAY’s study of residential water rates over the past 12 years for large and small water agencies nationwide found that monthly costs doubled for more in 29 localities. The unique look at costs for a diverse mix of water suppliers representing every state and Washington, D.C. found that a resource long taken for granted will continue to become more costly for millions of Americans. Indeed, rates haven’t crested yet because huge costs to upgrade or repair pipes, reservoirs and treatment plants loom nationwide.

In three municipalities — Atlanta, San Francisco and Wilmington, Del. — water costs tripled or more. Monthly costs topped $50 for consumers in Atlanta, Seattle and San Diego who used 1,000 cubic feet of water, a typical residential consumption level in many areas. Officials in the three municipalities and elsewhere, however, say actual consumption is often lower. But conservation efforts counter-intuitively may raise water rates in some localities.

The trend toward higher bills is being driven by:

— The cost of paying off the debt on bonds municipalities issue to fund expensive repairs or upgrades on aging water systems.

— Increases in the cost of electricity, chemicals and fuel used to supply and treat water.

— Compliance with federal government clean-water mandates.

— Rising pension and health care costs for water agency workers.

— Increased security safeguards for water systems since the 9/11 terror attacks.

Via USA TODAY analysis: Nation’s water costs rushing higher