Pennsylvania American Water Co. reported that lab results indicate no signs of bacteria in its Norristown area water system on Thursday afternoon.
A boil water advisory that impacts about 18,000 of the company's customers could be lifted Friday.
The first set of samples were collected Wednesday at 11 locations within the six municipalities that are under a precautionary boil water advisory.
With the first set of "clean" results, the company collected a second set of samples Thursday from 11 locations within the same communities.
According to state Department of Environmental Protection guidelines, Pennsylvania American Water must have two consecutive days of "clean" test results before DEP will allow the boil advisory to be lifted.
If the second set of results also show no evidence of bacteria, the advisory could be lifted on Friday for the approximately 18,000 customers who are affected. The precautionary boil water advisory was issued late Tuesday when parts of the company's distribution system lost positive water pressure.
"The Norristown Water Treatment Plant has returned to normal production levels, plus our storage tanks have refilled to almost normal capacity," reported a company spokesman Thursday afternoon.
"The plant's average production is 10.5 million gallons per day, and our storage capacity consists of seven tanks ranging from 400,000 gallons to 2.8 million gallons, so the water system is back to full water pressure and adequate capacity."