Construction work on May 23 caused localized low pressure in the city of Mercer Island’s water supply system, affecting approximately 100 homes southwest of Island Crest Park. Door tags were placed at affected homes.

The city issued a news release and recommended that residents in those homes boil their water for the next 24-48 hours. To treat the affected area, water service was shut off for a short period.

The city tested the supply, and said it would inform residents when that testing is complete. The precautionary notice was issued because the low pressure may have allowed contaminants to enter the system.

Boiled or bottled water should be used for drinking, making ice, washing dishes, brushing teeth and preparing food until further notice, according to the city news release.

Customers with questions should call the Mercer Island Public Works hotline at 206-275-7608 or visit the city’s website.

Note: The original map was updated at 7:15 p.m. to reflect about 30 additional locations that were part of a separate planned water outage area (hydrant work) and were also door-tagged on Tuesday.

UPDATE (as of 6:45 p.m. May 24): The city received satisfactory test results from the lab, and lifted the advisory. Affected residents may use their water again, but are advised to first follow these guidelines:

• Flush pipes for five minutes by running the cold water tap at all faucets; for a residence with multiple levels, start at the top of the house.

• If discolored, run water until it is clear.

• Follow manufacturer’s instructions for appliances such as water filters and water softeners.

• Dispose of ice from automatic icemakers, make and discard 3 batches, then wash and sanitize trays.

Additional questions are addressed here by King County Public Health.