FERNDALE, Wash. — Whatcom County Fire District 7 (WCFD7) firefighters have found themselves dispatched to some residential structure fire calls with visible smoke during the last couple weeks. But it was eventually determined the smoke was the result of sewer line testing by City Public Works staff.
It was reported sewer testing would be conducted last week and testing appears to be continuing again this week (see map below).
Firefighters responded to a residence on Shannon Avenue last week after the occupant reported smoke in a laundry room. It was dispatched as a dryer fire but, according to firefighters who responded, the dryer was not being used at the time. After checking for other possible causes it was determined a pipe leading from the laundry room to the sewer was the source of smoke during sewer testing in the neighborhood.
There have been a few other similar structure fire dispatches since then, including 1 yesterday, November 19th, with visible smoke reported in and around the residence.
WCFD7 Fire Chief Larry Hoffman said the residents did the right thing by calling 911. “People should not hesitate to call 911 if they are concerned. We would rather respond to a false alarm than not respond quickly to an emergency.”
City staff say that when smoke from sewer testing appears inside a residence, it may be the result of a plumbing problem but is most likely the result of dried-out P-traps in rarely used locations. P-traps are typically found under a drain and are simply a dip in the pipe intended to capture debris and hold water. The water blocks sewer odor and gases from coming into the residence. But, in locations where water is not frequently run through a drain, it can eventually evaporate leaving the dry P-trap open, allowing sewer odors and gases, including test smoke, to get in to the building.
The “smoke” is actually a non-toxic, non-staining odorless but visible vapor according to city staff.
According to information found on the City’s website, sewer smoke testing will continue this week in some Ferndale neighborhoods as shown on the map below.