Septic Installer Test For Washington State
(WOSSA) EXAM Questions and Answers (Verified
Answers) Study Guide (latest version verified for
accuracy) | 2026 Latest!!
Required Minimum Liquid Volumes of Septic Tanks: (Single Family
Residence) Number of Bedrooms: Each additional bedroom over 4 - ANSWER-
Required Minimum Liquid Tank Volume in Gallons:
1000 gallons + 250 gallons Each additional bedroom over 4
Residential Volume of sewage tank: - ANSWER- For OSS treating sewage
from a residential source, other than one single-family residence, two hundred
fifty gallons per bedroom with a minimum of one thousand gallons
Non-residential volume of sewage tank: - ANSWER- For OSS treating sewage
from a nonresidential source, three times the design flow
Maximum Hydraulic Loading Rate Calculation - ANSWER- -Soil Type
-Soil Textural Classification Description
-Loading Rate for Residential Effluent Using Gravity or Pressure Distribution
(gal./sq. ft./day)
WAC 246-272A-0250 Installation (Only installers may construct OSS,
Installers Must:) - ANSWER- (a) Follow the approved design;
WAC 246-272A-0250 Installation (Only installers may construct OSS,
Installers Must:) - ANSWER- (b) Have the approved design in possession
during installation;
,WAC 246-272A-0250 Installation (Only installers may construct OSS,
Installers Must:) - ANSWER- (c) Make no changes to the approved design
without the prior authorization of the designer and the local health officer;
WAC 246-272A-0250 Installation (Only installers may construct OSS,
Installers Must:) - ANSWER- (d) Only install septic tanks, pump chambers, and
holding tanks approved by the department;
WAC 246-272A-0250 Installation (Only installers may construct OSS,
Installers Must:) - ANSWER- (e) Be on the site at all times during the
excavation and construction of the OSS;
WAC 246-272A-0250 Installation (Only installers may construct OSS,
Installers Must:) - ANSWER- (f) Install the OSS to be watertight, except for the
soil dispersal component;
WAC 246-272A-0250 Installation (Only installers may construct OSS,
Installers Must:) - ANSWER- (g) Cover the installation only after the local
health officer has given approval to cover; and
WAC 246-272A-0250 Installation (Only installers may construct OSS,
Installers Must:) - ANSWER- (h) Back fill with six to twenty-four inches of
cover material and grade the site to prevent surface water from accumulating
over any component of the OSS.
Holding Tank Sewage System (HTSS): a - ANSWER- Is an alternative to a
conventional on-site sewage system with very special and limited applications.
Simply, the HTSS provides a means to collect and temporarily store sewage
from a facility or dwelling, for subsequent removal and transport to an approved
treatment and disposal site.
Holding Tank Sewage System (HTSS): b - ANSWER- A HTSS is an on-site
sewage system that incorporates a holding tank, the services of a sewage
,pumper/hauler, and the off-site treatment and disposal of the sewage generated
at the site served by the HTSS.
Holding Tank Sewage System (HTSS): Pemiting - ANSWER- The permit
should include specific information and requirements for pumping service
frequency and approved disposal of holding tank contents.
Holding Tank Sewage System (HTSS): Overflow Provisions - ANSWER- The
holding tank system must be designed and installed such that no overflow is
allowed, other than within the structure at the elevation of the lowest fixture
served.
Holding Tank Sewage System (HTSS): Surface Water - ANSWER-
Landscaping adjacent to the holding tank system should direct surface water
flow away from the tank and access points.
Holding Tank Sewage System (HTSS): Materials - ANSWER- Construction
materials used throughout the holding tank system must be able to function as
designed while exposed to sewage, sewage gases, and physical forces caused by
repeated tank filling and pumping which is inherent to system operation.
ANSI - ANSWER- American National Standards Institute
BOD - ANSWER- biochemical oxygen demand, typically expressed in mg/L.
CBOD - ANSWER- Carbonaceous Biochemical Oxygen Demand, expressed in
mg/L.
, FC - ANSWER- Fecal Coliform, expressed in number of colonies 100/ml.
LOSS - ANSWER- large on-site sewage system
NSF - ANSWER- Nation Sanitation Foundation International
O&G - ANSWER- Oils and Grease, component of sewage typically originating
from food stuffs (animal fats of vegetable oils) expressed in mg/L.
RS&G - ANSWER- Recommended Standards and Guidance
SSAS - ANSWER- a subsurface soil absorption system
TAC - ANSWER- Technical Advisory Committee established in WAC 247-
272A-0400
TN - ANSWER- Total Nitrogen, expressed in mg/L.
TSS - ANSWER- Total Suspended Solids. A measure of the total suspended
solids in a given solution, expressed in mg/L.
USEPA - ANSWER- United States Environmental Protection Agency
Additive - ANSWER- a commercial product added to an on-site sewage system
intended to affect the performance or aesthetics of an on-site sewage system
Approved - ANSWER- Acceptable to the authority having jurisdiction. Local
health officer or the department
(WOSSA) EXAM Questions and Answers (Verified
Answers) Study Guide (latest version verified for
accuracy) | 2026 Latest!!
Required Minimum Liquid Volumes of Septic Tanks: (Single Family
Residence) Number of Bedrooms: Each additional bedroom over 4 - ANSWER-
Required Minimum Liquid Tank Volume in Gallons:
1000 gallons + 250 gallons Each additional bedroom over 4
Residential Volume of sewage tank: - ANSWER- For OSS treating sewage
from a residential source, other than one single-family residence, two hundred
fifty gallons per bedroom with a minimum of one thousand gallons
Non-residential volume of sewage tank: - ANSWER- For OSS treating sewage
from a nonresidential source, three times the design flow
Maximum Hydraulic Loading Rate Calculation - ANSWER- -Soil Type
-Soil Textural Classification Description
-Loading Rate for Residential Effluent Using Gravity or Pressure Distribution
(gal./sq. ft./day)
WAC 246-272A-0250 Installation (Only installers may construct OSS,
Installers Must:) - ANSWER- (a) Follow the approved design;
WAC 246-272A-0250 Installation (Only installers may construct OSS,
Installers Must:) - ANSWER- (b) Have the approved design in possession
during installation;
,WAC 246-272A-0250 Installation (Only installers may construct OSS,
Installers Must:) - ANSWER- (c) Make no changes to the approved design
without the prior authorization of the designer and the local health officer;
WAC 246-272A-0250 Installation (Only installers may construct OSS,
Installers Must:) - ANSWER- (d) Only install septic tanks, pump chambers, and
holding tanks approved by the department;
WAC 246-272A-0250 Installation (Only installers may construct OSS,
Installers Must:) - ANSWER- (e) Be on the site at all times during the
excavation and construction of the OSS;
WAC 246-272A-0250 Installation (Only installers may construct OSS,
Installers Must:) - ANSWER- (f) Install the OSS to be watertight, except for the
soil dispersal component;
WAC 246-272A-0250 Installation (Only installers may construct OSS,
Installers Must:) - ANSWER- (g) Cover the installation only after the local
health officer has given approval to cover; and
WAC 246-272A-0250 Installation (Only installers may construct OSS,
Installers Must:) - ANSWER- (h) Back fill with six to twenty-four inches of
cover material and grade the site to prevent surface water from accumulating
over any component of the OSS.
Holding Tank Sewage System (HTSS): a - ANSWER- Is an alternative to a
conventional on-site sewage system with very special and limited applications.
Simply, the HTSS provides a means to collect and temporarily store sewage
from a facility or dwelling, for subsequent removal and transport to an approved
treatment and disposal site.
Holding Tank Sewage System (HTSS): b - ANSWER- A HTSS is an on-site
sewage system that incorporates a holding tank, the services of a sewage
,pumper/hauler, and the off-site treatment and disposal of the sewage generated
at the site served by the HTSS.
Holding Tank Sewage System (HTSS): Pemiting - ANSWER- The permit
should include specific information and requirements for pumping service
frequency and approved disposal of holding tank contents.
Holding Tank Sewage System (HTSS): Overflow Provisions - ANSWER- The
holding tank system must be designed and installed such that no overflow is
allowed, other than within the structure at the elevation of the lowest fixture
served.
Holding Tank Sewage System (HTSS): Surface Water - ANSWER-
Landscaping adjacent to the holding tank system should direct surface water
flow away from the tank and access points.
Holding Tank Sewage System (HTSS): Materials - ANSWER- Construction
materials used throughout the holding tank system must be able to function as
designed while exposed to sewage, sewage gases, and physical forces caused by
repeated tank filling and pumping which is inherent to system operation.
ANSI - ANSWER- American National Standards Institute
BOD - ANSWER- biochemical oxygen demand, typically expressed in mg/L.
CBOD - ANSWER- Carbonaceous Biochemical Oxygen Demand, expressed in
mg/L.
, FC - ANSWER- Fecal Coliform, expressed in number of colonies 100/ml.
LOSS - ANSWER- large on-site sewage system
NSF - ANSWER- Nation Sanitation Foundation International
O&G - ANSWER- Oils and Grease, component of sewage typically originating
from food stuffs (animal fats of vegetable oils) expressed in mg/L.
RS&G - ANSWER- Recommended Standards and Guidance
SSAS - ANSWER- a subsurface soil absorption system
TAC - ANSWER- Technical Advisory Committee established in WAC 247-
272A-0400
TN - ANSWER- Total Nitrogen, expressed in mg/L.
TSS - ANSWER- Total Suspended Solids. A measure of the total suspended
solids in a given solution, expressed in mg/L.
USEPA - ANSWER- United States Environmental Protection Agency
Additive - ANSWER- a commercial product added to an on-site sewage system
intended to affect the performance or aesthetics of an on-site sewage system
Approved - ANSWER- Acceptable to the authority having jurisdiction. Local
health officer or the department
