A primer on how to keep our aquifer fresh and clean

Maintaining our septic systems makes all kinds of sense.

Editor’s Note: This commentary by Susan McCabe is part of The Beachcomber’s ongoing series of “Green Briefs”, presented in partnership with the Whole Vashon Project. Find out more about the organization’s work at wholevashonproject.org.

As we look ahead to spring, it’s also time to check on our septic systems.

It’s all about the water. Our water is held in a sole-source aquifer system. Everything we put into the ground, flush down our toilets, or run down our sink drains eventually goes into Puget Sound, so we are responsible for treating our sewage. We need properly designed and maintained septic systems for a healthy aquifer system.

Maintaining our septic systems makes all kinds of sense.

Proper maintenance saves the higher cost of septic system failure. It protects plants and wildlife by preventing harmful pollutants from getting into the local ecosystems. It helps to protect property values as well as the health of the entire community, including your household. And, in the long-term, it protects Puget Sound and island water quality.

Once we use the water coming into our homes it becomes sewage. Island sewage only has a few options — it can be collected and piped to the wastewater treatment plant; it can stay at home and be treated in your own backyard septic system, or in some instances, it might be combined with the neighbors’ wastewater and be taken care of in a community system.

Most Vashon homes have septic systems — a little wastewater treatment plant in your yard. You’ll know you have a septic system if the waterline coming into your home doesn’t have a meter, if your water bill doesn’t include a sewer charge, or if your neighbors have septic systems.

You’ll find tank lids or ‘manhole covers’ above the septic tank, which is a buried, water-tight container usually made of concrete, steel, or plastic. Its job is to hold the wastewater long enough to allow solids to settle to the bottom forming sludge, while less dense material including oil and grease floats to the top as scum.

You can find your property’s septic system by going here. Under the “Resources for Residents” section, click on OSS Records and follow the instructions to find your OSS drawing. That will tell you details about your septic system.

Whatever system you have, it moves that wastewater through pipes into the soil, where microorganisms consume its nutrients and send it into groundwater, thus removing harmful bacteria, viruses, and other substances naturally. A properly treated system supports the natural bacteria — heroes of the septic system — that break down waste and keep deadly pathogens out of the water. It’s kind of magical — unless the drain-field gets overloaded, producing septic disaster!

You can prevent septic disaster simply by having a septic professional inspect and pump your tank regularly. The frequency depends on your system type, tank, and household size, how much wastewater and solid waste you generate — typically every three years.

Proper maintenance can make a septic system last almost 40 years. You’ll know it’s pumping time if the bottom of the scum layer is within six inches of the bottom of the T-shaped outlet from your tank, or if the top of the sludge layer is within 12 inches of the outlet. You’ll be able to check your system if you keep the tank lids accessible; don’t bury or build over them. Plant shallow root vegetation in your drain field.

Between inspections you can keep those microorganisms happy and working hard in a variety of ways:

  • Keep your household water flow low. Spread out water usage as much as possible, especially laundry (avoid running multiple loads at once).
  • Redirect water from your roof drains or yard away from the septic system drain field.
  • Compost food scraps to keep them out of the septic system.
  • Throw excessive soaps, oils, and greases into the trash.
  • Keep strong chemicals, cleaners, and additives out of the system.
  • Cover your drain field with grass or other appropriate plants.
  • Use your garbage disposal sparingly or not at all; it uses lots of water and adds more solids to the system causing it to fill faster.
  • And remember – toilets are not garbage cans. Only flush poop, pee, and toilet paper.
  • Watch for signs of dreaded septic system failure. Call a septic system professional if:
  • Wastewater backs up into household drains.
  • You see bright green, spongy grass on the drainfield, especially during dry weather.
  • Water or muddy soil pools around your septic system or in your basement.
  • There is a strong odor around the septic system.

Know how old your system is and plan ahead to replace it if needed. King County is a good source for technical and financial help when your septic system needs repairs or replacement.

If you find your septic system needs either, you may be eligible for financial assistance. Call King County at 206-455-8050. And for more information, check out Public Health, King County and Seattle kingcounty.gov/oss.

This commentary is adapted from King County’s “Vashon User’s Manual” a King County Public Health publication authored by McCabe and distributed by mail last year to all Vashon households.