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The City of Portland, Oregon

Portland Water Bureau

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How do you clean your pipes? We used an ice pig.

Crews conducting the ice pigging testIn May, our water quality team tried out a new technology to clean the inside of our water mains: ice pigging.

Similar to how we use a toothbrush to remove the biofilm that grows on our teeth, ice pigging uses an ice slushy to gently scrub the inside of the pipe. This scrubbing removes the biofilm normally present in the water mains throughout our system, without impacting the integrity of the pipe. Biofilm, while generally harmless to humans, can have negative impacts on water quality.

We are testing out this technology to measure its benefits in our system and see if it would be a useful tool to use in areas that need a deep cleaning or are challenging to clean using traditional flushing methods.

Site Selection

The site we chose for this ice pigging trial is a four-block stretch of water main that is watched closely by our water quality engineers. Because this particular stretch of water main is located on a dead-end street with only a few homes, the water doesn’t pass through the pipe quickly, which results in biofilm. The presence of the biofilm uses up the disinfectant in the water more rapidly than at other locations in our system. The goal of the ice pigging to is remove the biofilm and provide a long-term improvement of the water quality at this location.

Ice pigging truckRecipe for an Ice Pig

Ice pigging itself is accomplished by creating a briny ice slush that is then injected into the water main and pushed through the pipe by water from a nearby hydrant.

As the ice pig moves through the pipe, it collects the material it scrubs off the inside of the pipe and pushes it out through another pipe connected to the other end of the water main.

The ice pig and the material it collects is then disposed of into the sanitary sewer system.

The Results

The immediate results at our trial were dramatic with a lot of material cleaned out of the pipe. But the real test will be in the months and years to come as our water quality engineers continue to keep a close eye on the water quality in this location.


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