A North Shore Cornerstone Guide From ServiceMaster Restoration By Simons

This morning, I (Sam Simon, of ServiceMaster Restoration By Simons) walked into a massive historic church in Wilmette, Illinois to assess what was thought to be a small odor problem in one room. But the moment the doors opened, the issue became clear: the entire building reeked of sewage, despite no visible flooding, no toilets overflowing, and no backed-up drains.

The church staff noticed it too. They had no water on the floor. No wet carpets. No sewage leaks. Just an overpowering sewer gas smell that had seemingly filled every hallway, office, and sanctuary.

Their first question is the same one we hear from homeowners in Wilmette, Evanston, Skokie, Glenview, and across Chicago:

“How can my house or building smell like sewage when there’s no sewage backup?”

This cornerstone guide explains the real causes — the ones plumbers and restoration professionals see every day — and what you should do before that foul odor becomes a structural or health problem.

Understanding Sewer Gas: What You’re Actually Smelling

Sewer gas is not “just a bad smell.” It’s a mix of:

• Hydrogen sulfide (rotten egg smell)
• Methane
• Ammonia
• Water vapor
• Other organic byproducts

Even low levels can cause:

• Eye irritation
• Nausea
• Headaches
• Fatigue
• Respiratory irritation

At higher concentrations (rare but possible in enclosed spaces), methane can be explosive and hydrogen sulfide can be dangerous.

So if you smell sewage — even with no backup — treat it seriously.

The Top Reasons Your Building Smells Like Sewage With No Visible Backup

1. Tree Roots Have Entered the Sewer Line (EXTREMELY COMMON IN WILMETTE)

Wilmette, Evanston, Skokie, Kenilworth, and nearly all North Shore towns have older sewer infrastructure and large mature trees. Roots infiltrate clay sewer laterals, creating:

• Partial obstructions
• “Micro-backups”
• Slow wastewater movement
• Pressure changes in the line

This doesn’t always cause sewage to spill onto the floor.
Instead, it causes sewer gases to push back through drains, especially floor drains and toilets.

Signs roots may be involved:

• Odor is strongest in the basement
• Gurgling sounds from drains
• Odor changes when you run water
• Smell appears after rain

What typically needs to happen:

• Camera scoping of the line
• Rodding or hydro-jetting
• Possible RootX treatment
• Long-term maintenance every 1–2 years

In the Wilmette church I visited, this was the most likely culprit: roots + partial blockage + pressure imbalance = building full of sewer odor.

2. A Partial Main Line Blockage (Without Full Flooding)

A sewage backup isn’t always an “all or nothing” event.
Many buildings experience partial blockages from:

• Grease
• Scale
• Debris
• Flushable wipes
• Paper buildup
• Pipe corrosion
• Offset joints

When the main line slows down, air cannot move properly through the system. This causes pressure to push gases back into the structure instead of letting them escape through the roof vent.

Classic symptoms:

• Slow sinks
• Bubbling toilets
• Sulfur smell near drains
• Odor strongest after heavy water use

This is a plumbing emergency, even if the floors are still dry.

3. Dried-Out P-Traps (The Most Common “Invisible Odor” Source)

In unused bathrooms, storage rooms, mechanical rooms, and basements — something as simple as a dry P-trap can fill an entire home or business with sewer odor.

Why?
The trap water evaporates, removing the gas barrier.

Most frequently dried traps:

• Basement floor drains
• Utility sinks
• Mop sinks
• Overflow drains
• Unused showers

Fix:

Pour 1–2 cups of water into the drain, then a teaspoon of mineral oil to slow evaporation.

4. A Faulty or Broken Toilet Seal

A dried-out or cracked wax ring can allow sewer gas to escape from around the base of a toilet even when the toilet appears to function normally.

Signs:

• Smell near one bathroom
• Toilet wobbles
• Slight water staining around the base

A cheap repair — but a high-impact source of odor.

5. Blocked or Improperly Functioning Roof Vent

Plumbing vents release sewer gas outside.
But if the vent is blocked by:

• Leaves
• Ice
• Dead animals
• Bird nests
• Debris
• Snow (in Chicago winters)

Pressure in the drain system forces odor back inside.

Signs:

• Gurgling drains
• Odor strongest after flushing
• Smell appears only on certain floors

This is a plumber + roof technician scenario.

6. Sump Pump Pit Odor (Often Mistaken for Sewage)

Many North Shore homes have sump pits to control groundwater. If the pit lid isn’t sealed, gases from the drain tile — or even the storm sewer — can enter the home.

Older Wilmette and Evanston homes sometimes tie the drain tile system into the sewer line. That means your sump pit can carry sewer odor even without a backup.

7. Hidden Cracks or Leaks in Sewer Lines Beneath the Slab

A cracked sewer line under the floor can release gases into carpeting, tile, subfloors, and wall cavities.
Signs include:

• Odor limited to one room
• Smell increases after running water
• No visible moisture
• Insect activity
• Warm flooring in one spot (if line is leaking)

These require scoping and sometimes excavation.

Case Study: The Wilmette Church With No Backup But Intense Sewer Odor

Today’s real-world example perfectly illustrates this topic.
The church:

• Had no standing water
• Had no clogged toilets
• Had no visible sewage
• Had horrible sulfur/sewer gas odor throughout the entire structure

After walking the lower level and mechanical rooms, the most likely issue was:

Root intrusion + partial blockage + dried traps in unused areas.

A building this size has dozens of floor drains — many unused.
The P-traps had likely dried out during seasonal closures, allowing sewer gas to rise throughout the building.

Combined with partial sewer restriction from roots, the gases had nowhere to go but inside.

This is exactly why Odor Mitigation and Odor Neutralization Services are so essential for large facilities like:

• Churches
• Schools
• Park district buildings
• Commercial offices
• Condos and multifamily buildings
• Municipal buildings

Odor is a sign of a deeper plumbing issue — and the gas itself can permeate porous materials.

What You Should Do Immediately If Your Home or Building Smells Like Sewage

Step 1 — Run water into all drains

This recharges P-traps.

Step 2 — Flush unused toilets

Restores the water seal.

Step 3 — Pour water into the basement floor drains

Critical in Chicago/North Shore homes.

Step 4 — Ventilate the area

Open windows and doors if possible.

Step 5 — Call a licensed plumber to scope the line

Especially in Wilmette, Evanston, Skokie, Glenview, and Oak Park, root intrusion is extremely common.

Step 6 — Contact ServiceMaster Restoration By Simons for odor mitigation if the smell has permeated surfaces

Sewer gas can cling to:

• Carpets
• Furniture
• Walls
• HVAC systems
• Ceiling tiles
• Clothing, bedding & soft goods

We use negative air, odor-neutralizers, hydroxyl generators, and, when needed, structural cleaning to fully eliminate the odor.

Professional Odor Mitigation Services (What We Do)

At ServiceMaster Restoration By Simons, we provide full odor assessment and remediation, including:

• Sewer gas odor identification
• Odor containment
• Hydroxyl and ozone treatments (as appropriate)
• HEPA air filtration
• Negative air containment
• Cleaning of HVAC ducts
• Cleaning of walls, ceilings, floors
• Deodorizing porous materials
• Post-plumber sanitation

We specialize in large, complex environments:

• Churches
• Synagogues
• Condos & multifamily buildings
• Schools
• Retail and commercial buildings
• North Shore estates
• Historical properties

Areas We Serve

We proudly serve homes and businesses across:

Chicago Neighborhoods

Lincoln Park, Lakeview, Uptown, Edgewater, Rogers Park, Albany Park, Irving Park, North Center, Ravenswood, Andersonville, and surrounding neighborhoods.

North Shore Suburbs:

Wilmette, Evanston, Skokie, Winnetka, Kenilworth, Glencoe, Highland Park, Highwood, Lake Forest, Lake Bluff, Northbrook, Glenview, Northfield, Deerfield, Riverwoods, Bannockburn.

Lake County:

Deerfield, Highland Park, Lake Forest, Lake Bluff, Libertyville, Vernon Hills, Lincolnshire.

Oak Park & River Forest + surrounding west suburbs:

Oak Park, River Forest, Elmwood Park, Forest Park, Berwyn, Addison, Carol Stream, Naperville

Our Full-line of Services

• Residential Water Damage Restoration
  https://servicemaster-restorationbysimons.com/restoration-services/residential/water
• Residential Mold Remediation
  https://servicemaster-restorationbysimons.com/restoration-services/residential/mold
• Fire Damage Restoration
  https://servicemaster-restorationbysimons.com/restoration-services/residential/fire
• Specialty Cleaning Services
  https://servicemaster-restorationbysimons.com/restoration-services/residential/specialty

About ServiceMaster Restoration By Simons

ServiceMaster Restoration By Simons is Chicagoland’s trusted leader in water damage, fire damage, mold remediation, and specialty cleaning. Founded in Chicago in 1929, ServiceMaster is the nation’s oldest restoration company, and our franchise brings over 40+ years of local experience to homes and businesses across Chicago, the North Shore, Lake County, and Oak Park/River Forest.

Our leadership team includes CEO Nasutsa Mabwa, and COO Sam Simon, an IICRC Master Fire & Water Restorer and co-author of RESTORE: A Complete Guide to Protecting Your Home As Your Most Valuable Asset available on Amazon https://www.amazon.com/dp/1952779529
We proudly hold the IICRC’s highest certifications and are active members of the Restoration Industry Association (RIA).

FAQs

Why does my house smell like sewage but nothing is backing up?

Because sewer gases are escaping through dried traps, partial blockages, faulty seals, or venting issues.

Can tree roots cause sewer odor without a backup?

Yes. Roots often create partial blockages that cause odor long before actual flooding.

Can sewer gas make you sick?

Prolonged exposure can cause irritation, nausea, and headaches, and in high concentrations can be hazardous.

Should I call a plumber or a restoration company first?

If there is no water backup, call a plumber first. If the odor has permeated, call us for odor mitigation.

Call ServiceMaster Restoration By Simons (North Shore, Chicago, Lake County)

For emergency odor mitigation, sewer odor investigation, or cleaning after a plumbing event, contact us 24/7.

Chicago Office
420 W. Huron Street, Chicago, IL 60654
(773) 376-1110

North Shore Office (Skokie)
8124 Ridgeway Avenue, Skokie, IL 60076
(847) 316-9145

Lake County Office (Deerfield)
790 Estate Dr Ste 200, Deerfield, IL 60015
(847) 316-9145

Oak Park & River Forest
1010 Lake Street, Oak Park, IL 60301
(708) 524-0304