Why Does Sewer Smell Come and Go?

If you‘ve noticed an occasional unpleasant odor in your home reminiscent of rotten eggs or sewage, you‘re not alone. Many homeowners deal with intermittent sewer smells that seem to appear and disappear randomly. While this can be alarming, in most cases it is a fairly easy issue to address.

In this comprehensive guide, we‘ll explore the common causes of transient sewer odors, tips for troubleshooting the source, solutions for eliminating the smell permanently, and when to call in a professional.

What Causes Intermittent Sewer Smells?

There are a few common culprits when it comes to sewer smells that come and go:

Build Up of Gases

Sewer gas is produced by waste and sewage decomposition. Gases like hydrogen sulfide, ammonia, methane and carbon dioxide can occasionally build up in pipes, especially older systems with low-flow. As pressure fluctuates, pockets of gas may be released into the home, creating a temporary smell.

Cracks or Leaks

Small cracks or loose fittings in waste pipes or around the base of your toilet can allow sewer gases to leak out. Since the leaks are minor, they may seal temporarily when the system pressurizes. Then when pressure drops again, more smells are released.

Vent Stack Issues

Vent stacks are important for allowing gases to escape from the sewer system to the outdoors. If the vents become blocked or damaged, gases can back up and then escape into the home intermittently.

Plumbing Trap Problems

Traps are the u-shaped pipes under sinks and tubs that hold water to block gases. If the water evaporates due to infrequent use or cracks, gases can escape. Refilling the traps causes temporary relief until water evaporates again.

Septic Tank or Sewer Line Trouble

Homes on septic systems can experience backups and overflows if tanks get overly full or clogged. Sewer municipalities can also have line breaks or blockages that allow gases to leak out.

Troubleshooting Intermittent Sewer Smells

Pinpointing the exact source of transient sewer smells can be tricky, but here are some tips:

• Walkthrough all bathrooms, laundry rooms, and the kitchen to try and isolate the source. Odors are often strongest at their origin.

• Inspect all drain pipes and toilets carefully for any cracks or evidence of leaks. Dye tabs can help detect small leaks.

• Check all vent stacks on the roof for blockages. Look for signs like corrosion or nesting insects.

• Test to see if sink or tub traps are holding water and refill them if needed.

• For septic system owners, inspect tanks for overflows and high water levels.

• Consider renting a thermal camera to check for temperature differences that may indicate leaks behind walls.

• Test air quality with gas detectors to determine if methane or hydrogen sulfide levels are elevated.

• Keep a log of when smells occur and what precedes them to try and find a pattern.

Solutions for Eliminating Intermittent Sewer Smells

Once the source has been identified, there are solutions available:

Unclog Blocked Drains

Use a plumbing snake, auger, or drain cleaner to remove built up debris, grease, hair, and other gunk in pipes. Prevent future clogs by pouring hot water and baking soda down drains monthly.

Seal Cracks and Leaks

Apply waterproof epoxy sealants or replace broken sections of pipe to close any openings sewer gas could be escaping from.

Install Proper Venting

Ensure vent stacks extend at least 12 inches above the roofline and clear any obstructions. Install an air admittance valve if traditional venting is not possible.

Address Septic Tank Issues

Have tanks pumped, clean inlet screens, and reduce water use to prevent overflows. Repair any damaged baffles or cracked tanks.

Repair Sewer Lines

Trenchless sewer line repair techniques like pipe relining can fix breaks, collapses, leaks, and root intrusion without digging.

Maintain Drain Traps

Periodically add water to fill sink, tub, and floor drains to prevent trap water seals from drying out. Consider trap primers.

When to Call a Sewer Gas Professional

While many intermittent sewer gas issues can be addressed with thorough troubleshooting and DIY methods, it‘s wise to call in professionals for:

• Persistent, strong sewer odors that don‘t dissipate.

• Evidence of major leaks, extensive vent blockages, or sewer line breaks.

• Inability to locate the odor source.

• Septic tanks that fail to drain or experience frequent overflows.

• Health symptoms like nausea or dizziness from exposure to gases.

The trained eyes, powerful equipment, and years of experience sewer and plumbing pros bring to the job can quickly pinpoint problems that may stump homeowners. They can advise on the most cost-effective solutions while keeping safety and proper building code compliance in mind.

The Dangers of Sewer Gas Exposure

While passing whiffs of sewer gases may just be an annoyance, larger volumes of exposure can cause legitimate health concerns. Hydrogen sulfide, methane, ammonia and other gases can irritate eyes and respiratory systems. Long-term exposure has been linked to headaches, fatigue, trouble breathing, and nausea.

In severe cases, very high concentrations can cause loss of consciousness and death due to asphyxiation and poisoning. It‘s critical to address any substantial sewer gas leaks promptly to avoid health risks. Ventilate areas well after leaks are repaired to clear out any lingering gases.

How to Pinpoint the Source of Odors

Tracking down the origin of sewer smells that come and go can be a process of elimination. Here are some helper tools:

• Odor Detectors – Available at hardware stores, these devices have a probe that can sniff out sewer gas concentrations in different areas to hotspot the source.

• Smoke Generators – Introducing safe smoke into drain and sewer lines can reveal leaks and cracks visibly when smoke escapes.

• Dye Strips – Plumbers use dye tablets and strips to tag water in toilet tanks and pipes. The colored water will leak out at the location of any cracks.

• Thermal Cameras – Infrared technology can detect temperature differences behind walls that may indicate sewer leaks.

• Gas Meters – For large areas, portable gas metering equipment can take air samples and analyze for sewage gases.

Preventing Intermittent Sewer Smells

Many sewer gas issues can be avoided with some simple preventative measures:

• Regular drain cleaning – Use baking soda, vinegar, and boiling water monthly to keep drains cleared.

• Proper venting – Ensure vents are free of debris and extend above roof level when installing.

• Water conservation – Fix any leaks and install low-flow toilets to avoid overwhelming septic systems.

• Trap maintenance – Periodically fill drain traps and consider installing trap seal primers in seldom used drains.

• Routine septic tank pumping – Pumping every 3-5 years prevents overflows and leaks caused by excessive solids buildup.

Why You Shouldn‘t Ignore Persistent Sewer Smells

A passing whiff of sewer odor every now and then may not be concerning, but persistent bad smells should never be ignored. Long-term exposure to gases like hydrogen sulfide and methane pose serious risks to your health and home.

Continued smells likely mean there is an ongoing leak or blockage issue permitting large volumes of gas to regularly enter your living space. This needs to be addressed immediately to avoid health effects and prevent potential explosions. If repeated DIY troubleshooting efforts don‘t locate and resolve the problem, calling a professional plumber or sewer repair company is strongly advised.

Sewer Gas: A Necessary Evil

While nobody wants to live with the odors and health hazards sewer gases can produce, they are a necessary byproduct of household plumbing systems. Being aware of the causes, troubleshooting tips, and solutions for intermittent sewer smells can help you act quickly to restore healthy indoor air quality when these occasional nuisances occur. With preventative maintenance and prompt repair of any serious issues, your home can remain gas-leak free.