Following test results Saturday, Canterwood Water Co. customers are being told to keep boiling drinking water.
Workers found E. coli in the water during a routine test Friday, and flushed the system with chlorine to kill it.
The results Saturday showed three of four samples tested positive for coliform but negative for E. coli, said Peninsula Light Co., the company that manages the system for Canterwood, near Gig Harbor.
Coliform bacteria are not likely to make residents sick, but can indicate other bugs in water linked to disease, according to the state Department of Health.
The Canterwood Golf and Country Club restaurant near Gig Harbor and 780 customers of the Canterwood Water Co. were affected.
Crews will keep treating the system with chlorine and test it again Monday. Results from that test are expected Tuesday afternoon.