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.
Table 1. ESTIMATED SEPTIC TANK PUMPING FREQUENCIES IN YEARS
(For year round residence)
Tank Size
(Gallons)
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
750
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
Household Size (Number of People)
Note: More frequent pumping needed if garbage disposal is used
For Service Call: 503-666-2280
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.
