Here is a statement issued by Illinois American Water early Wednesday morning.  No cause of the loss of pressure was named:

Illinois American Water has issued a boil water advisory for customers in the City of Grafton, excluding the Grafton Hills Area.  The community grade school is not affected.  

This boil water advisory is being issued in accordance with Illinois Environmental Protection Agency regulations.  Anytime water pressure drops below 20 pounds per square inch in any part of a community’s distribution system, a boil water advisory must be issued as a precaution to protect customers.

Customers in the area described above should bring their water to a rolling boil for five minutes before using for drinking or cooking.   Water is OK for bathing, washing and other common uses. The boil water advisory  will be in effect until water quality samples confirm that the water remains safe for consumption.  

Standard boil water advisories normally last 36 hours.  For additional information, customers may call Illinois American Water’s 24 hour customer service center at 1-800-422-2782.