Septic Installer Test For Washington State
(WOSSA) Exam 2026 Questions and
Answers
ANSI - Correct answer-American National Standards Institute
BOD - Correct answer-biochemical oxygen demand, typically expressed in mg/L.
CBOD - Correct answer-Carbonaceous Biochemical Oxygen Demand, expressed
in mg/L.
FC - Correct answer-Fecal Coliform, expressed in number of colonies 100/ml.
LOSS - Correct answer-large on-site sewage system
NSF - Correct answer-Nation Sanitation Foundation International
O&G - Correct answer-Oils and Grease, component of sewage typically
originating from food stuffs (animal fats of vegetable oils) expressed in mg/L.
RS&G - Correct answer-Recommended Standards and Guidance
SSAS - Correct answer-a subsurface soil absorption system
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,TAC - Correct answer-Technical Advisory Committee established in WAC 247-
272A-0400
TN - Correct answer-Total Nitrogen, expressed in mg/L.
TSS - Correct answer-Total Suspended Solids. A measure of the total suspended
solids in a given solution, expressed in mg/L.
USEPA - Correct answer-United States Environmental Protection Agency
Additive - Correct 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 - Correct answer-Acceptable to the authority having jurisdiction. Local
health officer or the department
BED - Correct answer-a soil dispersal component consisting of an excavation with
a width greater than 3 feet
Building Sewer - Correct answer-that part of the horizontal piping of a drainage
system which starts from the end of the building drain and which receives the
discharge of the building drain and conveys it to a public sewer, private sewer,
individual sewage disposal system or other point of disposal. It begins two feet
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,outside the building wall and conveys sewage from the building drain to the
remaining portions of the on-site sewage system.
Cesspool - Correct answer-a covered hole or pit for receiving drainage or sewage,
as from a house allowing liquid to seep into the surronding rock or soil
Conforming System - Correct answer-an on-site sewage system of component
meeting rules of: New construction requirements
Approved and installed within previous requirements
Permitted by WAC-246-272A-0420
Cover Material - Correct answer-Soil placed over dispersal component, made up of
mineral material with no greater than 10% organic content. Cover may contain
organic surface material, an organic landscaper to help reduce and contain soil
erosion.
Cuts and Banks - Correct answer-a naturally occurring or artificially formed slope
greater than one hundred percent (forty-five degrees) and extending vertically at
least five from the toe of the slope to top of the slope.
Department - Correct answer-Washington State Department of Health
Designer - Correct answer-Person who matches site and soil characteristics with
approved components
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, Design Flow - Correct answer-Means the maximum volume of sewage a residence,
structure or other facility is estimated to generate in a twenty-four hour period. It
incorporates both an operating capacity and a surge capacity for the system during
periodic heavy use events. The sizing and design of a on-site sewage system
component is based on the design flow.
Development - Correct answer-The creation of a residence, structure, facility,
subdivision, area, or similar activity resulting in the production of sewage.
Disinfection - Correct answer-The process of destroying pathogens in sewage
through the application of chlorination, ultra-violent light, or ozonation.
Distribution Technology - Correct answer-any arrangement of equipment and/or
material that distributes sewage within and on-site sewage system.
Drainfield - Correct answer-subsurface soil absorption system, and soil dispersal
component
Drainrock - Correct answer-cleaned washed gravel or crushed rock ranging in size
from 3/4" to 2.5", and containing no more than two percent by weight passing a US
No.8 sieve and no more than one percent by weight passing through a US No. 200
Sieve.
©COPYRIGHT 2025, ALL RIGHTS RESERVED 4
(WOSSA) Exam 2026 Questions and
Answers
ANSI - Correct answer-American National Standards Institute
BOD - Correct answer-biochemical oxygen demand, typically expressed in mg/L.
CBOD - Correct answer-Carbonaceous Biochemical Oxygen Demand, expressed
in mg/L.
FC - Correct answer-Fecal Coliform, expressed in number of colonies 100/ml.
LOSS - Correct answer-large on-site sewage system
NSF - Correct answer-Nation Sanitation Foundation International
O&G - Correct answer-Oils and Grease, component of sewage typically
originating from food stuffs (animal fats of vegetable oils) expressed in mg/L.
RS&G - Correct answer-Recommended Standards and Guidance
SSAS - Correct answer-a subsurface soil absorption system
©COPYRIGHT 2025, ALL RIGHTS RESERVED 1
,TAC - Correct answer-Technical Advisory Committee established in WAC 247-
272A-0400
TN - Correct answer-Total Nitrogen, expressed in mg/L.
TSS - Correct answer-Total Suspended Solids. A measure of the total suspended
solids in a given solution, expressed in mg/L.
USEPA - Correct answer-United States Environmental Protection Agency
Additive - Correct 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 - Correct answer-Acceptable to the authority having jurisdiction. Local
health officer or the department
BED - Correct answer-a soil dispersal component consisting of an excavation with
a width greater than 3 feet
Building Sewer - Correct answer-that part of the horizontal piping of a drainage
system which starts from the end of the building drain and which receives the
discharge of the building drain and conveys it to a public sewer, private sewer,
individual sewage disposal system or other point of disposal. It begins two feet
©COPYRIGHT 2025, ALL RIGHTS RESERVED 2
,outside the building wall and conveys sewage from the building drain to the
remaining portions of the on-site sewage system.
Cesspool - Correct answer-a covered hole or pit for receiving drainage or sewage,
as from a house allowing liquid to seep into the surronding rock or soil
Conforming System - Correct answer-an on-site sewage system of component
meeting rules of: New construction requirements
Approved and installed within previous requirements
Permitted by WAC-246-272A-0420
Cover Material - Correct answer-Soil placed over dispersal component, made up of
mineral material with no greater than 10% organic content. Cover may contain
organic surface material, an organic landscaper to help reduce and contain soil
erosion.
Cuts and Banks - Correct answer-a naturally occurring or artificially formed slope
greater than one hundred percent (forty-five degrees) and extending vertically at
least five from the toe of the slope to top of the slope.
Department - Correct answer-Washington State Department of Health
Designer - Correct answer-Person who matches site and soil characteristics with
approved components
©COPYRIGHT 2025, ALL RIGHTS RESERVED 3
, Design Flow - Correct answer-Means the maximum volume of sewage a residence,
structure or other facility is estimated to generate in a twenty-four hour period. It
incorporates both an operating capacity and a surge capacity for the system during
periodic heavy use events. The sizing and design of a on-site sewage system
component is based on the design flow.
Development - Correct answer-The creation of a residence, structure, facility,
subdivision, area, or similar activity resulting in the production of sewage.
Disinfection - Correct answer-The process of destroying pathogens in sewage
through the application of chlorination, ultra-violent light, or ozonation.
Distribution Technology - Correct answer-any arrangement of equipment and/or
material that distributes sewage within and on-site sewage system.
Drainfield - Correct answer-subsurface soil absorption system, and soil dispersal
component
Drainrock - Correct answer-cleaned washed gravel or crushed rock ranging in size
from 3/4" to 2.5", and containing no more than two percent by weight passing a US
No.8 sieve and no more than one percent by weight passing through a US No. 200
Sieve.
©COPYRIGHT 2025, ALL RIGHTS RESERVED 4
