We find the exact source of that persistent sewer smell — vent, trap, wax ring, or line break — before any repair work begins.
You've scrubbed the bathroom twice. You've poured bleach down the drain. You've replaced the air freshener three times this month. And the sewer smell in your Markham home is still there — usually worse in the morning, or right after you run hot water.
That's because the smell isn't coming from anything you can clean. It's coming from a plumbing issue your nose detected before any other system in the house did.
At Koda Plumbing Service Co, sewer odor diagnostics is its own discipline. We don't treat it as an add-on to drain cleaning, and we don't guess at vent stacks until something works. We follow the smell to its mechanical source and document what we find before we touch a wrench.
Sewer odor is rarely random. In most Markham, IL homes we inspect, the cause falls into one of these categories:
The water seal in a rarely-used drain has evaporated, and sewer gas is now venting straight into your living space.
Gases that should be exiting through the roof are escaping inside walls or attics.
Sewer gas leaks around the base of the toilet every time you flush.
Under slab or yard — often brings pests and is expensive to ignore.
Common in basements or laundry rooms where fixtures are rarely used.
We use combustible gas indicators and smoke testing to pressurize the system and reveal exactly where sewer gas is escaping. No invasive demolition.
Get Diagnosed Today →We scope the line, isolate the section producing the odor, and treat or repair the actual cause.
Get Diagnosed Today →We test the seal, flange, floor moisture, and verify the vent. Especially important for basement and guest bathrooms.
Get Diagnosed Today →We keep diagnostic slots open every weekday for fast-response inspections in Markham.
We inspect with proper protective equipment and gas detection tools.
Our diagnostic process is the same for every home.
When does the smell appear? Where is it strongest?
Every fixture, traps, cleanouts, gas readings.
When needed, followed by written findings.
A common pattern: a homeowner calls a plumber for a bad drain smell, gets a drain cleaning, the smell goes away for two weeks, and then it returns. The reason is usually mechanical, not biological.
Drain cleaning addresses buildup — but if the underlying issue is a vent problem, partial pipe collapse, or failed seal, the smell rebuilds.
The fix is sequencing: Diagnose first, clean second.
In low concentrations, it's primarily an irritant — headaches, nausea, eye irritation. In higher concentrations it becomes a health risk. Persistent sewer gas should be addressed.
A standard diagnostic visit runs 60 to 90 minutes. Complex cases involving smoke testing or camera work can take 2 to 3 hours.
Not for sewer odor work. We'll give you a flat diagnostic fee on the call, and a written repair quote after the inspection.
Outdoor sewer smells usually trace back to a damaged exterior cleanout, yard line break, or municipal issue. We diagnose and coordinate when needed.
Yes. Every odor diagnostic includes a return verification visit.
If a sewer smell in your Markham home has lingered for more than a week, schedule a documented diagnosis today.
(888) 466-2103You’ll receive a written report, photos, and clear repair options.