Saving your OSS: How routine septic maintenance can prevent costly repairs

By Adiam Mengis, Educator Consultant, Environmental Health Division

The fall rainy season can mean more stress on your on-site septic system. It’s a great time to think about how you’re maintaining your OSS to help prevent unnecessary and costly repairs.

Tens of thousands of King County homes and businesses use an OSS, a mini-water treatment facility right on the homeowner’s property. Designed, installed and maintained properly, onsite septic systems process wastewater from toilets, sinks, showers, washing machines and dishwashers without contaminating your property and neighborhood with sewage.

How do you know if you have an OSS?
Are you paying for sewer? If you are not, you likely have an OSS. Learning about your OSS is important as each system design may require different maintenance in order to protect your investment. To get a copy of your OSS records, start by searching here.



Don’t flush it and forget it – or you may regret it
It’s important to regularly maintain your OSS, even if you have no signs of system failure. Your OSS may last for decades if properly maintained. Fixing or replacing a failing OSS can be very expensive compared to routine maintenance. While it costs $250 and up to pump the average septic tank, repair or replacement of the septic system ranges from $3,000 to $20,000 or even higher depending on the complexity of the OSS and its location. Regular maintenance of your OSS is also the law and could result in liability if not up to date.

Dos and Don’ts to keep your OSS working properly


  • Inspect and regularly pump-out your septic tank as needed and/or every 3-5 years.
  • Keep septic tank lids easily accessible and secured.
  • Quickly repair all leaky faucets and toilets.
  • Use water efficiently; for example, use “low flow” fixtures on faucets and shower heads.
  • Spread laundry washing throughout the week and wash full loads.


  • Don’t flush anything except toilet paper into your septic system.
  • Don’t flush wipes, diapers or feminine products (even if the products indicate they are flushable).
  • Don’t flush medicines down the drain.
  • Don’t run dishwashers and washing machines at the same time.
  • Don’t pour fats, grease, solids or toxic materials (like household chemicals).
  • Don’t use septic tank additives.
  • Don’t drain water from hot tubs in to your septic system.
  • Don’t park vehicles on your septic system and drain-field.

Worried your OSS may need repair or replacement? There is financial assistance to repair septic systems. Typical system failure signs include backed-up waste water, odor, spongy grass and water around the septic tank and drain-field. The following loan sources may be available for qualifying individuals:

  • Craft3 Clean Water Loan Program
    Craft3 provides clean water loans to repair or replace failing onsite sewage. Learn more and apply at or contact Craft3 at and 888-231-2170.
  • King County Housing Repair Program
    King County Housing Repair Program provides interest-free loans and emergency grant services to low and moderate-income home owners and individual low-income renters with disability who reside in King County, outside the City of Seattle. Call 206-263-9095 and check the website for more details.
  • USDA Rural Housing Services Program
    The USDA Rural Housing Services Program provides loans to low-income homeowners. Call 360-428-4322 ext. 4 or visit their website.

Check out these links to get more details on properly maintaining our OSS:

Originally posted on September 22, 2017.

2 thoughts on “Saving your OSS: How routine septic maintenance can prevent costly repairs

  1. My system seems to be working fine but I noticed that the grass over the tank is a lighter color than the surrounding grass and makes a round patch of lighter color. Does this indicate a leak in the system and if so what is the remedy?

    1. Without being on site it is not possible to say that the tank is not leaking. With that said, we look for lush green grass, not lighter colored when looking for leaks. I would guess that the tank is shallow and the soil used to backfill was not of good quality. If this is the case, we recommend adding risers to grade and adding some good quality soil in this area to help the grass grow. For additional resources on maintaining your on-site sewage system follow this link to the King County Maintenance and resources page:

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