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Professionals who can help - on-site sewage/septic systems

Find information for professionals to work on your on-site sewage/septic system.

OSS rule revision process

Recently, the Washington State Board of health approved changes to statewide OSS rules. Now, King County is updating our local codes to make sure they comply with the state’s changes.

Stay informed by signing up for our code revision newsletter. You can also read our August edition.

Only individuals with Certificates of Competency or licenses are authorized to perform work and maintenance on septic systems. Below are lists of licensed and certified professionals in King County.

OSS designers and professional engineers (84 KB)

Design new and replacement septic systems, submit applications for subdivisions and boundary line adjustments.

Master installers (39 KB)

Install new and replacement septic systems.

On-site system maintainers (124 KB)

Inspect and maintain septic systems and make limited repairs.

Certified liquid waste pumper/haulers (57 KB)

Pump waste from tanks and haul it to a wastewater treatment plant.

Questions to ask professionals before hiring

Please use these questions to gather the information you need when hiring someone to work on your septic system.

We recommend contacting at least 3 septic professionals before deciding whom to hire. You may also contact our office if you have more questions.

On-site wastewater treatment system designers or professional engineers

Ask these professionals the following questions:

  • What is the price of the following? (some of these services may be included in one fee):
    • Preliminary site evaluation
    • Soil log digging
    • Design
    • Stub-out inspection
    • Pressure test
    • Installation inspection
    • Backfill inspection
    • As-built package
  • Does this include the County fees?
  • Does your company assist with recording a Notice on title?
    The Notice on Title is a document in which the owner acknowledges the property is served by a septic system and is responsible for its operation and maintenance.
  • Do you charge extra for the Homeowner's manual?
  • Do you charge for extra visits or consultations?
  • How quickly do you submit the final record drawing after the septic system is installed?
  • What is your turnaround time for returning calls and emails?

Certified master installers

These experts install new and replacement septic systems. During your consultation, ask them these questions:

  • What is the price of the installation?
    • Does this include electrical work?
    • Does this include County fees?
    • Does this include the final inspection?
    • Does this include backfill labor and materials?
    • Does this include the As-built package?
  • How long is the bid good for and what does it include?
  • Do you fill the tanks with water after installation?
  • Does your company offer monitoring services? If not, who do you recommend?
  • Does your company try to prioritize weather-sensitive systems?
  • What is your approximate schedule for installation from the time you receive the permit?
  • Does your company assist in the Notice on Title that needs to be recorded?
    The Notice on Title is a document in which the owner acknowledges the property is served by a septic system and is responsible for its operation and maintenance.
  • Do you guarantee your work? What is your warranty period? Will you complete repairs if there is a problem?
  • Who is your certified master installer that will be on site to oversee the install of the septic system?
  • What is your turnaround time for returning calls and emails?

Tip: For a repair, the installer should inspect the property and determine the cause of failure prior to any proposals.

Certified on-site sewage system maintainers

These professionals inspect and maintain septic systems and make limited repairs. Ask them the following questions:

  • What will the OSM inspection include (for example, checking baffles and for leaks, cleaning filters, structural integrity and drainfield checks, etc.)?
  • Can I be present for the inspection? (We recommend that you track the work done by the maintainer and learn more about how your septic system is functioning.)
  • Do you charge extra to uncover lids that are buried?
  • What are the benefits to installing risers to the surface (if needed)?
  • Do you offer any discounts (for example, senior, new customer, or others)?
  • Does the inspection cost include county fees?
  • When will the report be entered in onlineRME for viewing?
  • If repairs are needed, can you perform the repairs? Can you do electrical repairs, or do you work with an electrician?

TIP: If a maintainer finds a problem with the septic system, you will need to get that fixed. You can hire anyone who is certified to do the type of work that is needed.

Liquid waste pumpers/haulers

These experts pump waste from tanks and haul it to a wastewater treatment plant. During your consultation, ask them these questions:

  • What is the price of the pump-out? What does the pump-out include?
  • If the septic tank is over 1,000 gallons, will it cost extra?
  • Do you offer any discounts (for example, senior, new customer, or others)?
  • When will the report be entered in OnlineRME?
  • Does this cost include digging to uncover the septic tank lid(s)? If not, how 
    much do you charge to dig out:
    • 1 septic tank lid
    • 2 septic tank lids
    • Pump tank lid - If there is a pump tank, it should be pumped in addition to the septic tank, rinsed with a hose, and pumped dry. If the pump tank is very full, you may be charged an extra fee.
  • Does this cost include dumping and county fees?
  • Does this cost include inspection of the inlet and outlet baffles in the septic
    tank? Do you charge extra to clean the filter baffle?
  • Is there an additional charge for the extra water and time required to pump a tank that has an unusual amount of scum or sludge?

TIP: Let the pumper know the size, type, accessibility of lids, age of the house, and last 
time the system was pumped.

If you have a long-distance to pump over or will require pumping up a steep slope, provide the distance and elevation to the pumper. The pumper will determine whether the truck can provide this type of service.

Download these questions as pdf (123 KB)

These questions are available for download in multiple languages:

在雇用工人处理您的化粪池系统时,请使用以下这些问题来收集您需要的信息 (Chinese, simplified) (226 KB)

在僱用工人處理您的化糞池系統時,請使用以下這些問題來收集您需要的信息 (Chinese, traditional) (328 KB)

Вопросы для домовладельцев (Russian) (196 KB)

Su'aalo loogu talagalay Mulkiilayaasha (Somali) (171 KB)

Preguntas para propietarios (Spanish) (182 KB)

Các Câu Hỏi Dành Cho Người Chủ Sở Hữu (Vietnamese) (219 KB)

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