Ferndale residents living north of Thornton Road and west of Vista Drive may be surprised to see wisps of smoke emerging from unexpected places next week. The City of Ferndale Public Works Department has scheduled sanitary sewer smoke testing from Monday, September 21 through Friday, September 25, and wants residents to know what to expect before work begins.
What Smoke Testing Is and Why It Matters
Sewer smoke testing is a standard diagnostic technique used by public works crews to find places where groundwater or surface water is seeping into the sanitary sewer system. When rainwater infiltrates sewer pipes through cracks, faulty connections, or deteriorating joints, it adds volume to the system that wastewater treatment plants were not designed to handle. That extra flow, called inflow and infiltration, can overwhelm treatment capacity during heavy rain events, cause sanitary sewer overflows, and drive up operating costs for the utility and ultimately for ratepayers.
To find the problem spots, crews introduce a non-toxic, non-staining, and odorless smoke-like vapor into the sewer system through manholes. The smoke travels through the pipes under slight pressure and escapes wherever there is a defect or opening. By watching where smoke appears at the surface, crews can pinpoint leaks, broken laterals, and improper connections that would otherwise be invisible underground.
The City of Ferndale uses this method periodically across different parts of the sewer system as part of its infrastructure maintenance program. The September 21 to 25 window targets the area north of Thornton Road and west of Vista Drive, which covers established residential neighborhoods in that part of the city.
What Residents May See and Should Not Be Alarmed By
Because the sewer system is interconnected throughout the testing area, it is not possible to predict exactly where the smoke vapor will surface. Residents may see smoke coming from roof vents, gutters, yards, building foundations, manhole covers, cleanouts, or other unexpected locations both inside and outside their homes or businesses.
Smoke appearing from roof vents is completely normal and is one of the most common visible signs of a properly functioning smoke test. It does not indicate a problem with the building. The vapor is engineered specifically to be safe: it contains no toxic compounds, leaves no stains, and disperses within a few minutes in open air.
The testing vapor does not create a fire hazard. However, if you see smoke and are genuinely uncertain whether it is from sewer testing or an actual fire, call 911. Crews will be in the area and can be reached through the city if you want confirmation before calling emergency services, but erring on the side of calling 911 for anything that looks like a real fire is always the right instinct.
How to Prepare Your Home Before Testing Begins
There is a simple step residents can take to minimize the chance of smoke vapor entering their home or business: run water into every drain. Pour water into floor drains, infrequently used sinks, showers, laundry tubs, and any other fixtures that may have dried out. The water fills the P-trap, which is the curved section of pipe beneath the drain, creating a water seal that blocks the sewer gas and smoke vapor from traveling up into the living space.
Drains that go unused for weeks or months are the most common path for smoke to enter a building. Floor drains in basements, utility rooms, and garages are particularly prone to drying out. A few cups of water poured into each drain before Monday morning is all it takes to maintain the barrier.
If smoke does appear inside a building despite these precautions, it typically points to a plumbing defect such as a missing cleanout cap, a broken or disconnected drainpipe, or a missing P-trap. Crews will note these locations during testing and the city may follow up with property owners about repairs.
Schedule and Weather Dependence
Testing is scheduled to run Monday through Monday, September 21 to 25, but the schedule is weather dependent. Rain, strong winds, or other field conditions can cause crews to pause or reschedule portions of the work. Residents should be aware that the testing window may shift slightly if conditions are not favorable early in the week.
For questions or concerns before, during, or after testing, contact City of Ferndale Public Works at 360-685-2379. The department can answer questions about the process, confirm whether testing is happening in a specific location on a given day, or take reports about smoke appearing in unexpected locations that may indicate a plumbing issue worth investigating. More information about the city's infrastructure programs is available at the City of Ferndale website.
Similar sewer smoke testing was conducted in parts of Bellingham last month, according to city records. Ferndale's program follows the same methodology and safety standards. For background on other infrastructure and utility work affecting Whatcom County roads and services this fall, earlier coverage tracked PUD pipeline replacement work that has been affecting western Whatcom County roads in recent weeks.
