Emergency Hotline 503-666-2280

Septic Tank Design Gresham Oregon & Surrounding Areas

Goodman Sanitation in Portland, OR knows the correct design of a septic tank system is all-important for proper wastewater treatment and to protect groundwater quality. A septic system is more than just what we all know of as the watertight septic tank that receives the wastewater from a home plumbing system. It is followed by a drainfield (ie: leach bed) made up of a network of perforated pipes that distribute the treated water into the soil for final treatment.

Different soil types require different septic tank system designs to function efficiently. Where soil is made up of clay or bedrock with a shallow water table, the septic system needs to be elevated about the surface. This is called a "mounded" system and ensures there is enough unsaturated, permeable soil providing adequate filtration for the wastewater before it ultimately reaches the groundwater table.

In other areas like flood zones located close to rivers and other bodies of water with already saturated soil, a more advanced wastewater treatment system may be required to sufficiently treat the wastewater. These systems add oxygen or "aerate" the wastewater. In addition, there are also advanced wastewater treatment systems that help neutralize disease germs prior to their reaching groundwater levels by using peat moss-based or chlorinating chambers.

Septic tanks come in a variety of different sizes. Goodman Sanitation will determine the correct size for your home depending on how much wastewater is being generated. Factors that determine wastewater usage are how many individuals live in the home, how often a washing machine is used, whether there is a garbage disposal in use, and what materials are being introduced into the wastewater. We also provide education on water conservation and what wastewater practices will keep your septic system healthy.

Houshold size (Number of People)
Tank Size
1 2 3 4 5 6 7 8 9 10
500 5.8 2.6 1.5 1.0 0.7 0.4 0.3 0.2 0.1 -0.7
500 9.1 4.2 2.6 1.8 1.3 1.0 0.7 0.6 0.4 0.3
1000 12.4 5.9 3.7 2.6 2.0 1.5 1.2 1.0 0.8 0.7
1250 15.6 7.5 4.8 3.4 2.6 2.0 1.7 1.4 1.2 1.0
1500 18.9 9.1 5.9 4.2 3.3 2.6 2.1 1.8 1.5 1.3
1750 22.1 10.7 6.9 5.0 3.9 3.1 2.6 2.2 1.9 1.6
2000 25.4 12.4 8.0 5.9 4.5 3.7 3.1 2.6 2.2 2.0
2250 28.6 14.0 9.1 6.7 5.2 4.2 3.5 3.0 2.6 2.3
2500 31.9 15.6 10.2 7.5 5.9 4.8 4.0 4.0 3.0 2.6

Note: More frequent pumping needed if garbage disposal is used


Provided through a grant from the Farmer Home Administration. The material is the result of tax supported research and as such is not copyrightable. It may be freely reprinted with the customary crediting of sources.

Extension Services, Oregon State University, Corvallis, O.E. Smith, director.
This publication was produced and distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914. Extension work is a cooperative program of Oregon State University, the U.S. Department of Agriculture, and Oregon counties.
Oregon State University Extension Service offers educational programs, activities, and materials – without regard to race, color, national origin, sex, age, or disability – as required by Title VI of the Civil Rights Act of 1964, Tax IX of the Education Amendments of 1972, and Section 504 of the Rehabilitation Act of 1973. Oregon State University Extension Service is an Equal Opportunity Employer.


There are inspections for homeowners who want to remodel their homes with additions to the house or property.

There are inspections for hardship cases for homeowners who want to add a mobile home to the property and attach to the existing septic system.

There is the "time of transfer" inspection / evaluation when the homeowner is selling the property.

Each of these inspections require that the tank be uncovered, the distribution box(es) be uncovered, that there is an amount of water introduced to the tank, to watch the contents flow to the distribution box and be accepted by a "thirsty" drainfield, to pump the tank and note any deficiencies.

To do an inspection on any and all pump vault components and panels along with electrical connections. To provide a detailed plot plan meeting all DEQ Specified requirements with all DEQ forms filled in completely with our technicians "certified" number and identification on the reports.

Should any repairs be needed to help bring your system "up to date" with compliance codes. We will outline the repairs and the cost and schedule an appointment for you. This gives you time to make an informed decision, ask questions, research websites, or ask for comparison bids for repair or work on fitting the repairs into your budget.

Your septic system is the second biggest investment, next to your home and Goodman Sanitation will be considerate on how you spend your money.