What You Need to Know About Commercial Building Sewer Line Issues
43% of Our Clients Are Concerned About Commercial Sewer Lines — Here’s What You Need to Know
According to our scheduling data, 43% of our clients express concern about sewer lines during commercial property inspections. This might seem like a smaller percentage compared to roofs or HVAC, but make no mistake—when sewer lines fail, the consequences are messy, costly, and disruptive.
In this blog, we’ll cover:
Why sewer lines are a common concern
5 major sewer-related issues we find in commercial buildings
What our commercial sewer line inspection includes
How to protect your property from sewer system failures
Let’s dive into the hidden (and often smelly) world beneath your building’s floor.
Why Sewer Lines Worry Property Owners
Unlike more visible systems, sewer lines are completely hidden—but when they fail, it’s impossible to ignore. Here’s why they’re a key concern for investors, tenants, and property managers:
1. They’re Difficult (and Expensive) to Replace
Sewer lines run under the slab or in crawlspaces. Repair often requires breaking concrete, disrupting tenants, and incurring major costs.
2. Backups Are Disruptive and Hazardous
A clogged or broken line can result in wastewater backup into tenant spaces—leading to sanitation hazards, mold growth, and business interruption.
3. Many Lines Are Decades Old
Commercial buildings constructed before 1980 often use cast iron or clay piping, which are prone to corrosion, collapse, and tree root intrusion—especially when the system has been neglected.
4. They’re Rarely Inspected Until There’s a Problem
Sewer lines are out of sight and mind until a backup occurs. Unfortunately, that usually means damage has already been done.
5 Common Sewer Line Issues in Commercial Buildings
We regularly uncover these sewer-related problems during commercial inspections—some obvious, some hidden:
1. Corroded Cast Iron Drain Lines
Older buildings often have cast iron drain systems that are severely corroded inside. This leads to slow drains, frequent clogs, and eventual pipe failure.
2. Sewer Gas Odors
If traps dry out or vents are improperly installed or blocked, sewer gases may enter occupied spaces. This not only smells terrible—it can indicate more serious ventilation problems or even health risks.
3. Bellies and Back-Pitched Lines
Improper slope during original construction or building settlement over time can cause low spots (“bellies”) or reverse slopes in drain lines. These areas collect waste and water, leading to buildup and clogs.
4. Unvented or Poorly Vented Fixtures
Without proper venting, drains work inconsistently—gurgling, draining slowly, or siphoning traps dry. This is a code violation and a functional headache.
5. Patchwork Repairs and Improper Materials
DIY fixes often involve dissimilar materials (like cast iron joined to PVC with duct tape or improper couplings). These setups leak, shift, and fail under load.
What Our Sewer Line Inspection Includes
While we don’t perform full plumbing diagnostics during a commercial inspection, we do visually inspect and test accessible portions of the system—and we strongly recommend further evaluation when warning signs are present.
✔ Visual Inspection of Exposed Drain Lines
In basements, crawlspaces, and mechanical rooms, we inspect all visible horizontal and vertical drain lines for corrosion, leaks, improper slope, and material condition.
✔ Functional Testing of Plumbing Fixtures
We operate a representative number of toilets, sinks, floor drains, and commercial fixtures to observe water flow, drainage speed, and unusual behavior (like gurgling or bubbling).
✔ Odor and Moisture Detection
We document sewer gas odors, musty smells, and visible signs of long-term leaks, such as efflorescence on walls or slab staining.
✔ Review of Plumbing Vents
When visible from the or roof level, we check vent stacks for damage or obstruction. We also assess whether every fixture appears to be properly vented.
✔ Recommendations for Sewer Scope
When signs of backup, slow drainage, or aging materials are present, we recommend a video sewer scope inspectionby a licensed plumber to verify line condition under the slab.
✔ Opinion of Cost and Risk Assessment
If we observe advanced corrosion, suspicious odor patterns, or multiple symptoms of drain failure, we include a non-binding Opinion of Cost and risk level assessment.
How to Protect Your Building From Sewer Line Failure
Here’s how commercial building owners and facility managers can reduce the risk of a surprise failure:
➤ Schedule a Sewer Scope for Older Properties
If the building was built before 1985 or has had chronic drain issues, a scoped inspection of interior and exterior sewer lines is a worthwhile investment.
➤ Maintain Drain Traps
Unused fixtures (especially in janitor closets, floor drains, or vacant units) should be flushed regularly to keep traps filled and block sewer gases.
➤ Document All Plumbing Repairs
Maintain clear records of any plumbing modifications. Know what materials were used, and ensure all work was performed by licensed professionals.
➤ Don’t Ignore Sewer Smells
Even if it’s “just an occasional whiff,” a persistent sewer odor means something isn’t sealed, vented, or draining correctly. Address it before it escalates.
➤ Implement a Drain Maintenance Program
Periodic jetting of high-use or problematic lines—like those in restaurants or laundromats—can prevent grease and debris from forming chronic blockages.
Conclusion: Sewer Line Problems Are Out of Sight—But Not Out of Risk
A functioning sewer system is something most owners never think about—until it becomes a problem. With over 40% of our clients listing sewer lines as a concern, it’s clear these hidden systems deserve serious attention.
Whether you’re buying a property, managing tenants, or planning a renovation, understanding the condition of your sewer infrastructure is essential to avoiding emergencies, keeping tenants safe, and protecting your investment.
Need a Sewer Line Assessment or Sewer Scope Referral?
Out of sight doesn’t mean out of risk. Sewer line failures can turn into expensive, hazardous emergencies—especially if they aren’t caught early. With 43% of our clients expressing concerns about sewer systems, you're wise to take action now.
At Focus Building Inspections, we assess your building’s sewer infrastructure and recommend proactive steps to protect your tenants, operations, and investment. Get clarity and confidence before hidden problems bubble to the surface.
Book your commercial inspection or contact our team for an expert evaluation. We’ll inspect what’s visible, test what we can, and refer you to trusted specialists for deeper diagnostics if needed.
Questions This Article Answers
Why are sewer lines a significant concern during commercial property inspections?
What are the consequences of sewer line failure in commercial buildings?
What common issues do inspectors find with commercial sewer systems?
How do aging materials like cast iron and clay affect sewer line reliability?
What are the signs that a sewer system may be compromised?
What does a commercial sewer line inspection from Focus Building Inspections include?
Why is a sewer scope recommended for older commercial properties?
How can property owners proactively maintain sewer systems and prevent failures?
What are the risks of DIY plumbing repairs and improper sewer system fixes?
Why is it important to address sewer gas odors immediately?
Bibliography / Resources
American Society of Heating, Refrigerating and Air-Conditioning Engineers. (n.d.). Plumbing system performance standards. ASHRAE. Retrieved April 25, 2025, from https://www.ashrae.org/technical-resources/plumbing-systems
Environmental Protection Agency. (n.d.). Wastewater infrastructure in commercial buildings. EPA. Retrieved April 25, 2025, from https://www.epa.gov/sustainable-water-infrastructure
International Association of Certified Home Inspectors. (n.d.). Inspecting drain, waste, and vent systems. InterNACHI. Retrieved April 25, 2025, from https://www.nachi.org/plumbing.htm
International Code Council. (2021). Plumbing and sewer code sections. ICC. Retrieved April 25, 2025, from https://codes.iccsafe.org/codes/i-codes
Plumbing Manufacturers International. (n.d.). Drainage system design and best practices. PMI. Retrieved April 25, 2025, from https://www.safeplumbing.org