Spring Cleaning inside the Westhill Water Tank

A three-man NUD crew recently spent a wet week in the belly of a steel beast 142 feet high and 67.3 feet around.

Every five years, each one of our water tanks gets a deep clean pressure wash inside. This year it was Westhill’s turn, our largest tank located at 19100 88th Ave NE in Bothell.

How do we empty and clean a 3 million gallon tank? Very carefully. First we drain the water slowly, over the course of one to two days, to avoid affecting water pressure levels. In the emptied tank, crews walk along a specially-built access gangway (photo below) to shoot high pressure water along the tank floor and lower walls, rinsing away dirt and sediment. Although treated at the Tolt water source before it reaches NUD’s pipes, any water source will naturally contain dirt particles that settle at the bottom of pipes and storage containers. Think of a Britta water filter, only on a much larger scale.

Once cleaned, the tank is then very carefully refilled. Our water quality officer keeps close track of water quality data to ensure the proper temperature, pH and chlorine residual levels are maintained.

On a side note, our crew members do practice climbing the 140 foot ladder to the top of the tank. Even with protective climbing gear, it can be quite scary!

Thanks to our crews hard work, Westhill now has a fresh interior shine. The outside will get it’s own scheduled summer cleaning.


Interested in seeing inside a water tank? Watch this short video clip, footage courtesy Lead Utility Worker Willie Anderson. (The noise in the background is the pressure washer).