The boil-water notice was issued in accordance with Texas Commission on Environmental Quality regulations because of low water pressure throughout much of Houston's supply, Mayor Sylvester Turner said at a media briefing.
The low pressure, caused by a massive 96-inch main line break midday Feb. 27, leads to a greater risk of bacterial growth, Harris County Judge Lina Hidalgo said. However, the city's current water supply is safe and the notice is regulatory requirement from the state that is ordered when pressure dips below a certain level, said Jeff Weatherford, Director of Transportation and Drainage Operations at the City of Houston at the media briefing.
The notice affects most of the city inside Beltway 8 and does not affect the Kingwood and Clear Lake areas, which are not served by the mainline that burst Feb. 27, Turner said.
Residents in Bellaire, West University Place and Southside Place are also on alternative water supplies, according to officials, and would not be subject to the notice.
Officials also urged Houston residents to conserve water while the break is resolved.
The main break has already caused a number of closures and Mayor Turner said any restaurant that does not have running water must cease operations immediately.
Harris County Public Health has a set of precautions outlined when residents are recommended to boil water. The Feb. 27 recommendation to boil water applies only to city of Houston users and excludes Kingwood and Clear Lake area residents.
Editor's note: this post has been updated for clarity.