A boil water advisory was issued Thursday afternoon for residents of Upper Leacock Township.
The township said in a notice on its website that residents should not drink water without boiling it first.
"We will notify you when the water is safe to drink," the notice, published at 2:15 p.m., said.
The township did not say why the boil water advisory was issued.
The notice included boiling instructions: "Bring all water to a boil, let it boil for one minute, and let it cool before using, or use bottled water.
"Boiled or bottled water should be used for drinking, making ice, brushing teeth, washing dishes and food preparation until futher notice.
"Boiling kills bacteria and other organisms in the water."