How do I know if my septic system is failing?

A septic system can fail loudly, with an alarm sounding, or it can fail more quietly. If you hear your septic system alarm, call a service provider immediately; leave a message if you have to. You can usually turn the alarm off, but don’t let that silence lull you into forgetting you have a problem. An alarm can indicate an over-full tank, a back-up, or the failure of one or more system components.

When a septic system fails, untreated sewage can travel to places where it shouldn’t be. It can surface on the ground near the septic system, or back up into your home pipes, or seep into groundwater and marine water without any indication.

Signs of a failing system include:

  • Water or sewage backing up in toilets, drains, and sinks 

  • Slow draining bathtubs, showers, and sinks 

  • Gurgling sounds in the plumbing system

  • Standing water or damp spots near the septic tank or drainfield

  • Bad odors around the septic tank or drainfield

  • Bright green, spongy lush grass over the septic tank or drainfield, even during dry weather

  • Algal blooms in nearby ponds or lakes

  • High levels of nitrates or coliform bacteria in water wells

What should I do if I suspect a problem with my septic system?

Don't hesitate to call a professional. Addressing problems sooner rather than later helps to extend the life of the system and avoid contact with raw sewage. Most problems can be corrected with minor repairs. If a major repair or redesign of the system is required, King County will coordinate with the septic professional on permitting.

Who Should I call if I have a problem?

On Vashon, there’s:

 Greentree Dozing (206-463-3889) offers:

  • Maintenance Inspections 

  • Time of Sale Reports

  • Camera locates

  • Alarm response & diagnosis

  • Pump replacements & general system component repairs

  • Tank replacements

  • Tank pumping & abandonment

  • Design coordination


Niece Pumping (206-463-5969) offers:

  • Pumping

  • Inspections

  • Routine maintenance

  • Referrals to other professionals

Both Niece and Greentree offer operations & maintenance agreements


If you’re looking beyond Vashon, check out this list of King County Certified On-Site System Maintainers (OSM). 


Related Links:

Flowchart: Septic System Repair and Replacement Process