Ferndale residents east of Interstate 5 may notice something unusual coming from their roof vents, gutters, or manholes on Thursday and Friday: smoke. The City of Ferndale's Public Works crews are conducting sanitary sewer smoke testing on September 24 and 25 in the area east of I-5, from Main Street south to Smith Road.
The testing is a routine diagnostic tool that crews use to identify where surface water, groundwater, or stormwater is illegally entering the city's sanitary sewer system. When the wrong kind of water infiltrates the sewer system, it increases the volume of wastewater that must be treated at the municipal facility, raising costs and reducing capacity during heavy rain events. Finding and fixing those entry points protects both the sewer system and local waterways.
Why Smoke Testing Is Done
Sanitary sewer systems are designed to carry only household and commercial wastewater to the treatment plant. When groundwater, rainwater, or runoff finds its way into the system through cracked pipes, deteriorated joints, or improperly connected drains, it is called inflow and infiltration. High inflow and infiltration rates are a significant problem for many aging sewer systems across the Pacific Northwest, where heavy fall and winter rains can overwhelm treatment capacity if the infiltration is severe enough.
The consequences of unchecked inflow and infiltration extend beyond higher treatment costs. When excessive clean water enters the sanitary sewer, it mixes with actual sewage and must be conveyed to the treatment plant at full treatment cost, even though it arrived clean. During major storm events, the combined surge can push flows beyond what the treatment plant can handle, creating the risk of sanitary sewer overflows. Those overflows, in which partially treated or untreated sewage escapes the collection system, are a serious environmental violation and a direct threat to the streams, wetlands, and waterways that make Whatcom County worth living in. Proactive testing programs like this one are the primary tool utilities use to stay ahead of those situations.
Smoke testing works by pumping non-toxic smoke into the sewer lines under a slight positive pressure. The smoke travels through the pipes and escapes anywhere the system has a breach, a loose fitting, or an unauthorized connection. Technicians on the surface watch for smoke emerging from unexpected locations, such as yard drains that should not be connected to the sanitary sewer, cracks in the pavement above pipes, or gaps around manhole covers. Each location where smoke appears unexpectedly gives the crew a precise target for follow-up inspection and repair, making the process far more efficient than digging at random or waiting for a failure to occur.
The smoke used in this testing is completely safe. According to the City of Ferndale, the testing smoke is non-toxic, non-staining, odorless, and does not create a fire hazard. It is the same type of smoke used in sewer testing operations across the country and poses no health risk to residents or pets. The product leaves no residue on surfaces and dissipates quickly in open air, meaning any smoke visible in a yard or rising from a vent will be gone within minutes once the crew moves to the next test section.
Ferndale is not unusual in facing this kind of maintenance challenge. Many cities throughout Washington state operate sewer infrastructure that was built decades ago, and even relatively newer systems can develop infiltration problems as soils shift, tree roots intrude, and pipe joints age. Periodic smoke testing is considered a best practice by the water quality and public works industries precisely because it is non-destructive, fast, and highly effective at identifying problem locations before they escalate into costly failures or permit violations.
What Residents Should Do
If you live in the testing area, east of I-5 between Main Street and Smith Road, there is one practical step that can prevent smoke from entering your home through plumbing fixtures: run water into all sinks, showers, floor drains, and any other infrequently used drains before the testing begins. This ensures the P-traps in your plumbing are filled with water, which creates a seal that blocks smoke from traveling up through the drain into your living space.
Plumbing traps can dry out if a drain is not used regularly, and a dry trap offers no barrier to smoke. A simple fix is to pour a cup of water into any drain that has not been used in the past week or two, particularly utility sink drains in garages and basement floor drains. Homes with finished basements that include bathroom or laundry facilities should pay particular attention to floor drains in mechanical rooms or storage areas, which are among the most commonly neglected fixtures in residential plumbing.
Property owners who have added outbuildings, sheds, or accessory dwelling units with plumbing should also make sure those fixtures have water in their traps before the test window begins. Any structure connected to the sanitary sewer on your property falls within the scope of the testing, and unauthorized connections discovered during testing may require remediation at the property owner's expense.
Residents should not be alarmed if they see smoke emerging from their yard, roof vents, or nearby manholes during the testing window. That is exactly what the smoke is supposed to do. Roof vents, in particular, are a normal exit point for sewer gases in any home, and smoke appearing from those locations is a sign that the sewer line beneath the property is pressurized and connected to the test section, not a sign of any problem with your home's plumbing. However, if you see smoke and cannot confirm it is from the sewer testing rather than an actual fire, call 911. It is always better to verify.
Questions and Contact Information
The Ferndale Public Works department is the point of contact for residents with questions or concerns about the testing. They can be reached by phone at 360-685-2379. Staff can confirm the testing schedule, explain whether a specific address is within the testing zone, and advise on any steps residents should take based on their particular plumbing setup. Residents who have unusual or non-standard plumbing configurations, such as older homes that may have been connected to the sewer before current codes were established, may want to call ahead to understand whether their setup could trigger a follow-up inspection.
Ferndale's sewer system serves a growing community that has expanded significantly in recent years as development has accelerated both inside the city limits and in surrounding areas of Whatcom County. That growth puts additional pressure on existing infrastructure and makes routine diagnostic work like smoke testing even more important, because system capacity that might have been adequate a decade ago may now be approaching its limits during peak demand periods. Finding and sealing infiltration pathways is one of the most cost-effective ways to recover capacity without building new treatment infrastructure.
Routine maintenance and diagnostic work like this smoke testing also helps the city stay ahead of potential system failures before they turn into more costly emergency repairs or sewage spills. The cost of a targeted pipe repair or joint resealing identified through smoke testing is typically a fraction of the cost of emergency excavation and repair after a sewer main fails or backs up into homes. From a public finance perspective, programs like this one pay for themselves many times over by preventing the larger failures they are designed to catch.
For more on how Whatcom County municipalities protect local water quality and maintain public infrastructure, visit the Whatcom County watershed regulations page, which outlines rules designed to keep surface water out of both sewer systems and drinking water supplies across the county. You can also read about cleanup work happening along the Bellingham waterfront as part of the broader effort to protect local water quality.
