Your Septic Installation
Experts in Boring, Oregon

Bacteria are what make a septic system work. They break down waste, leaving the water clean enough to safely percolate down into the earth. The whole system is designed to keep bacteria healthy and busy. Some live in the tank, but most do their work in the septic drain field.

1. Household wastewater and sewage flow to the septic tank.
2. The watery liquid waste, called “effluent,” fills most of the septic tank. Anaerobic bacteria begin breaking down the organic material in the effluent.
3. Sludge falls to the bottom. Sludge is composed of inorganic solid waste like toilet paper and the byproducts of bacterial digestion.
4. A septic tank acts as a settling pond where greases and oils float to the top creating a scum layer. Heavier solids, the sludge, sink to the bottom.
5. A filter prevents most solids from entering the outlet pipe.
6. Effluent flows to the leach field or may be pumped via a tank pump if it is uphill or some distance away. The septic drain field provides a large area where bacteria can thrive and treated water can seep into the ground.
7. The drain field pipe is perforated to allow liquid to seep into the surrounding gravel. Gravel around pipes allows water to flow into the soil without becoming clogged.
8. Aerobic bacteria in gravel and soil complete the decomposition of the waste.
9. Clean water seeps down into the groundwater and aquifer.

Like many other things in life, the cost will vary depending on the size of the septic tank and the type of system required. A complete septic system—including a leach field (also called a drain field), tank, and piping- can range from $10,000 to $25,000.

The size of the septic tank and the septic tank materials will affect the cost. It is more expensive to remove and dispose of a cement septic tank than plastic tanks. There can also be additional costs for materials if your new tank requires a tank pump or aerobic systems. Labor typically makes up 50% to 70% of your total project cost. In a typical installation, labor is more expensive than the price of the tank itself. Whereas the tank size needed for a three-bedroom home to a four-bedroom home may cost $1,000 to $3,000, the septic tank installation cost can range from $1,500 to $6,000.

In the State of Oregon, septic tank capacity for a single-family home must be based on the number of bedrooms. For a home with 4 or fewer bedrooms, the tank capacity must be at least 1,000 gallons. Septic tank capacity must be at least 1,500 gallons for homes with more than four bedrooms.

A new septic system can be expected to last for 20-30 years. But how long a septic system lasts is influenced by a variety of factors such as the materials used and the maintenance of your septic tank systems.

The leach field is often left unused to prevent damage to the system, but there are many things you can (and can’t) put on your septic drain field.

Things you CAN put on the field:

• Shallow-root vegetation
• Open-air kennel
• Lightweight structures like playground equipment or volleyball nets
• Fences, as long as the posts are buried deep into the field

Things you CANNOT put on the field:

• Deep-root vegetation
• Vegetable gardens
• Structures such as sheds, decks, and garages
• Pools, ponds, or other water features

Anaerobic septic tanks are conventional systems where anaerobic (non-oxygen consuming) bacteria digest the solid waste. Once turned into wastewater, the waste exits the tank and goes to a large leach field.

Aerobic systems are more complex and often include a composting toilet and a continuous flow system. This septic system is more expensive than the traditional anaerobic type, but it’s more efficient. Because the effluent (or the sewage or wastewater) is of higher quality, these systems require a smaller leach field.

In a sand filter system, effluent flows from the septic tank to a pump chamber. It is then pumped into the sand filter. The sand filter is often PVC-lined or a concrete box filled with sand material. Effluent is pumped under low pressure through the pipes at the top of the filter where it then filters through the sand. The filtered wastewater is then discharged to the septic drain field.

Sand filters provide a high level of treatment for nutrients and are good for sites with high water tables or close to water bodies, but they are more expensive than a conventional septic system.

• Water and sewage from toilets, drains, and sinks are backing up into the home.
• Bathtubs, showers, and sinks drain very slowly.
• Gurgling sounds in the plumbing system.
• Standing water or damp spots near the septic tank or leach field.
• Bad odors around the septic tank or drain field.
• Bright green, spongy lush grass over the septic tank or drain field, even during dry weather.
• Algal blooms in nearby ponds or lakes.
• High levels of nitrates or coliform bacteria in water wells.