In the U.S. alone…
the EPA estimates that the backlog of water infrastructure replacements/upgrades is anywhere from $300 billion to $1 trillion. The current capital spending rates imply a that a pipe is replaced once every 700 years. As a result, by 2020, 60% of all water main pipes in the US will be classified as substandard.
There is an emerging understanding that point-of-use water filtration is a much more cost-effective method of providing potable water, compared to wholesale replacement of water infrastructure.
Sources: IFC “Safe Water for All – Harnessing the Private Sector to Reach the Underserved”; UNICEF; Times of India, November 2009; Citibank Global Water Sector handbook, May 2011