Reoccupying a building after an extended closure: Guidelines for protecting water quality.

When buildings are unoccupied for extended periods of time and water is not being regularly used, the water can sit and become stagnant, causing water quality to degrade over time.

Denver Water is sharing guidelines for businesses on how to clear or flush the water in a building’s internal water system before the building is reoccupied. These guidelines also include a link to similar guidelines from the Centers for Disease Control and Prevention.

The goal is to replace stagnant water in the building’s water system with fresh, high-quality water from Denver Water’s distribution system. Denver Water recommends working with your building’s engineer or facility manager for this process.

Guidelines: It is important to follow these in the order outlined below.

1. Turn on the cold water inside the building (break room sinks, drinking fountains, utility closets, restrooms, etc.) on each floor.
   1. Start from the furthest point away from where water enters the building (e.g., for a building with five floors, start on the fifth floor and work your way to the first floor.) Remember to run only the cold water.
   2. The cold water has been successfully flushed when you feel the water temperature go from slightly warm to cold.
2. Flush hot water storage tanks (boiler and/or hot water tanks per manufacturer’s flushing instructions) to displace stagnant/discolored water with fresh water.
3. Repeat step 1 using hot water.
   1. The hot water has been successfully flushed when you feel the water temperature turn from warm to hot.
4. Flush and perform preventative maintenance on point-of-use devices or systems, such as cooling towers, systems providing additional water treatment, etc., per the manufacturer’s recommendations as applicable.

Once all domestic water service lines, internal plumbing and point-of-use devices/systems are flushed/properly maintained, the building can be occupied.

The Centers for Disease Control and Prevention have also provided comprehensive guidelines for specific industries, such as hotels or restaurants.

Denver Water recommends working with your building’s engineer or facility manager for this process. If you have questions for Denver Water, please contact Customer Care Monday through Friday, from 7:30 a.m. to 5:30 p.m. at 303-893-2444.