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Sustainable Development

Onsite Wastewater Management Systems Program

Malfunctioning Systems

Some of the signs of a malfunctioning septic system include: 

  • Contaminated wells 

  • Untreated sewage discharging to streams and ditches 

  • A soft, smelly spot in the yard with lush grass growth 

  • Ponding or wet spots around the disposal fields

Not every sign of a malfunction is obvious. In improperly designed systems, untreated sewage can move for hundreds of feet from a home before contaminating the environment and/or posing a threat to public health. The offending property owner may not even know that a problem exists.

To protect public health and the environment, discharge limits are set and used to evaluate systems to make sure they stay in compliance with standards. Systems can be out of compliance because they are malfunctioning or are failing. The circumstances determine the actions that must be taken to bring the system back into compliance.

System Malfunctions
A system malfunction is associated with improper maintenance or operation. These problems can be corrected to bring the septic system back into compliance. With proper care, regular inspections, repairs, and occasional upgrades the system should work for decades to protect public health and the environment. Following the Maintenance Tips will help to avoid a system malfunction.

System Failures
A system failure occurs when the existing system cannot be repaired and must be replaced. If the soil conditions are suitable and space is available, a property owner may be able to construct another disposal field.  In some instances this is not an option and an alternate system, such as a holding tank or modified field, is required.   

A property owner may have a failing septic system for a number of reasons, with the most common being:

  • System was sited on unsuitable soil
  • System was poorly installed
  • System is old and has reached its life expectancy

Avoiding System Failures
Most failures can be avoided at the time of construction. The soil is the most important factor in any septic system installation.  The soil must be carefully characterized and protected during and after construction. A property owner can avoid a system failure in the following three ways:

  1. Conduct a detailed soil analysis to provide the basis for a good system design. Hire a trained soil evaluator to examine the site to make sure it is able to support a septic system. The soil evaluator will supplement information gathered from the soil with information from auger holes and probe samples and general information from soil surveys.
  2. Construct the system when the soil is dry.  Construction in wet soil can result in soil compaction and smearing that reduces the ability of the soil to absorb and treat wastewater.
  3. Do not pipe sewage to the ditch or storm sewer. Do not allow the construction of a shallow drain to carry untreated sewage to a ditch, drain tile, or storm sewer. If sewage is ponding in the yard, the problem should be corrected immediately.  If the system is beyond repair, a qualified professional should be retained to evaluate the site and design a new system. 


1.  Sewage backing up into house and/or plumbing fixtures not draining properly
Potential Causes Potential Remedies
  • Excess water entering system
  • Fix leaks
  • Improper plumbing
  • Install water-saving fixtures
  • Blockage in plumbing
  • Stop using garbage disposal
  • Improper operation
  • Clean septic tank and check pumps
  • Pump failurex
  • Replace broken or cracked pipes and remove roots
  • Improper system design
  • Seal pipe connections
  • Roots clogging pipes
  • Avoid willow trees near system
2. Sewage surfacing in yard
Potential Causes Potential Remedies
  • Excessive water use
  • Fix leaks
  • System blockages
  • Install water-saving fixtures
  • Improper system elevations
  • Clean septic tank and check pumps
  • Undersized soil treatment system
  • Consult professionals
  • Pump failure or improper operation
  • Fence off area until problem is fixed
3. Sewage odours-indoors
Potential Causes Potential Remedies
  • Sewage surfacing in yard
  • Repair plumbing 
  • Improper plumbing
  • Clean septic tank and check pumps
  • Dry drain traps
  • Replace water in drain traps
  • Sewage backup in house
  • Unsealed ejector sump pump
  • Roof vent pipe frozen closed
4. Sewage odours-outdoors
Potential Causes Potential Remedies
  • Source other than owner's system
  • Clean tank and chec pumps
  • Sewage surfacing in yard
  • Replace damaged caps
  • Inspection pipe caps damaged or removed
  • Repair or replace drainfield
5. Contaminated drinking or surface waters
Potential Causes Potential Remedies
  • System too close to well, water table, or fractured bedrock
  • Replace your well and/or septic system
  • Cesspool or drywell in use
  • Contact a local unit of government to investigate other potential sources
  • Sewage discharges to surface or groundwater
  • Improper well construction
  • Broken water supply pipe
  • Source other than homeowner's system
  • Broken sewage lines
6.  Distribution pipes and/or soil treatment system freezes in winter
Potential Causes Potential Remedies
  • Improper construction
  • Check construction
  • Check valve in lift station not working
  • Examine check valve and/or replace it
  • Foot or vehicle traffic over piping
  • Keep people and vehicles off area
  • Low flow rate
  • Increase water use
  • Back of use
  • Have someone use water in house if you are away
  • Undersized pump
  • Increase frequency of pump cycling
  • Operate septic tank as a holding tank
  • Pump system in fall and use carefully over winter months
  • Don't use antifreeze
7.  Effluent surfacing in absorption field
Potential Causes Potential Remedies
  • Absorption field is too small
  • Investigate the proper field size based on soil conditions and home wastewater output
  • If undersize, enlarge the existing or build a new one
  • Install water conservation devices such as low-flush toilets, low-volume showerheads and faucet aerators
  • Clogged soil absorption field

  • Replace existing absorption field and/or install a second field if the lot size permits.  Rotate field annually.
  • A seasonally high water table saturates soil and causes the systemt o become sluggish or fail during rainy periods



  • Install interceptor drains to lower or divert the hight water table
  • Use water conservation practices
  • Modify system using shallow placement of trench alternatives
  • Build an alternative system such as a low-pressure pipe system
  • Solids carry over from septic tank clogs field
  • Pump the tank and check baffles
  • Leaky faucets increases hydraulic load on the field
  • Maintain plumbing in good repair
8.  Plugged house sewer vent (soil stack)
This problem can make sewer lines drain so slowly that solids settle out
Potential Causes or Symptoms Potential Remedies
  • Sewer gas smell around the house and/or gurgling sound as air is pulled through the trap into the sewer when drains are used.
  • Enlarge undersize, broken, or plugged vents.  In winter, check for ice build-up on vents
  • Install roof vent extenders if snow accumulations covers the existing vent year after year.
9.  Blockage between the house and septic tank
Potential Causes Potential Remedies
  • Blockage may be in the house sewer

  • Remove blockage with sewer tool
  • If roots have penetrated pipe joints, reseal pipe joints after routing
  • Scum layer could be septic inlet
  • Pump the tank
  • Check inlet baffles after pumping tank
  • Blockage that recurs in a new system is likely caused by improperly installed sewer line(s)
  • Reconstruct the sewer line(s) using the correct slope
  • Blockage that recurs in a previously trouble-free system is likely caused by a broken pipe connection
  • Locate and replace broken pipe


10.  Blockage between septic tank and absorption field
Potential Causes Potential Remedies
If the liquid in the septic tank is higher than normal, look for:
  • Plugged tank outlet.  In older tanks the outlet baffles can collapse, causing scum and solids to overflow and plug the outlet or the line to the absorption field
  • Pump the tank 
  • After pumping the tank, route the line and replace defective baffles
  • Obstruction in the line from the tank to the field.  This is most likely caused by solids overflowing from the tank, root penetration, or collapse of a pipe section
  • Pump the tank
  • After pumping the tank route the line and replace defective baffles