Wastewater maintenance

The City of Redmond Wastewater Maintenance Division maintains and operates the wastewater (sewer) system to meet customers' needs. The wastewater system serves a residential population of 77,490 (2023) within the City limits and approximately 3,500 residential households in the Novelty Hill area. They are also responsible for maintenance and repair of over 230 miles of pipe ranging from 8 to 36 inches in diameter, 15 miles of easements, 7,336 manholes, and 22 pump stations.Vactor truck cleaning vault

Maintenance activities include but are not limited to:

  • Closed-circuit television (CCTV) inspection
  • High-pressure hydro-cleaning
  • Easement and pump station maintenance
  • Daily monitoring of the SCADA (Supervisory Control and Data Acquisition) system
  • Activities related to providing excellent customer service

Wastewater Division staff repair lift stations, pipes, and manholes. Lift station repair involves complex electrical circuits, pumps, and equipment. Manhole repairs range from frame and cover replacement to entire channel and bench restoration. Pipeline repairs range from open trench pipe replacement to slip lining damaged sections of pipe.

City staff maintains the wastewater system in a manner that protects public investment, the environment, and human health to ensure compliance with state and federal mandates.


You may be surprised to know that the City of Redmond Wastewater Maintenance Division is a front-runner when it comes to the use of existing and emerging technologies. Wastewater staff use a wide variety of hardware and software to efficiently operate and maintain City infrastructure. Listed below are just a few of those technologies. 


SCADA stands for Supervisory Control and Data Acquisition. Quickly defined, SCADA is a computerized system which monitors and controls infrastructure. Redmond's Wastewater Division makes use of this technology to monitor 22 lift stations remotely.


GIS stands for Geographic Information System. GIS integrates hardware, software, and data for capturing, displaying, and analyzing all forms of geographic information. GIS allows Wastewater Division staff to visualize, question, interpret, and understand data.


GraniteNet software allows city staff to complete digital video inspections of underground wastewater pipe with a Closed-Circuit Television (CCTV) truck. These inspections allow staff to determine what maintenance procedures are necessary for each segment of the wastewater pipe.

Lift Stations

What is a lift station?

Due to hills and valleys in the landscape, sewer systems include locations where sewage needs to be pumped from low points to higher elevations, from which it will ultimately flow via gravity to a King County treatment plant. Once sewage arrives at the treatment plant it is treated and discharged to Puget Sound.

Lift Station Upgrade Program

What: Lift Station

Replace or rehabilitate ten wastewater lift stations in six years. At the program's start, the Sewer Utility owned and operated 23 lift stations throughout its service area (see map for locations) stations identified for replacement are numbered). With the completion of the Lift Station 14 abandonment project, there are now 22 wastewater lift stations.

When: Now–2023

Why: If a lift station fails, there is a risk that raw sewage will back up into homes or businesses or overflow into Lake Sammamish and other natural waterways. Ten wastewater lift stations are at, or past, their useful life. Mechanical and electrical equipment in lift stations usually lasts 20-30 years. Some lift stations are over 30 years old, some are failing now, and some have equipment for which replacement parts are no longer available.

How: The sewer lift stations will be replaced or rehabilitated using sewer rates, development connection charges, and bonded debt so that the stations are in good working order by 2025.

Progress:  In 2019, Lift Station 2 was replaced, Lift Station 14 was abandoned, and a new sewer line was installed. Lift Station 3 was replaced in 2020. Lift Station 13 work started in 2020 and is expected to be completed in 2023. Also, in 2021, work on Lift Station 12 started, and completion is expected in 2023. Five lift stations are currently in design for targeted equipment upgrades in 2023.

Homeowners Responsibilities

Maintain Your Side Sewer

Side sewer infographic for homeownersSewage from your side sewer can back up into your house and yard when the pipes get clogged. This can happen when water or roots fill your drain, so never plant trees or bushes in these areas. Never flush trash or put fats, oils, and grease (FOG) down the drain to avoid this problem.

Backups are preventable by keeping rain out of your side sewer and not flushing or putting materials down your drain. To determine if your side sewer is blocked, ask your plumber or contractor and make repairs as needed.


No Flush Wipes cropped iconDon't Flush Them

Even if it says flushable wipes can clog pipes and create costly repairs.

Why can't "flushable wipes" be flushed?

Flushable wipes are not environmentally friendly because they are made of plastic and do not break down in the wastewater system.

Fats Oils and Grease (FOG) Butter melting in a pan

Never pour FOG down your drain. Instead, cool it, can it, and put it in the trash. FOG in your pipes can solidify, backup, and cause costly repairs and damage to your house.

Grease Disposal

Lady Pouring Grease Into a Container

Pour cooled leftover oil into a sealable container

Pouring or washing down used cooking oil down the drain will clog and damage pipes. 

  • Put cooled oil from fryers, pots, or pans in a sealed container.
  • After solidifying in a container, it can go into the garbage.
  • Don’t pour it down the drain, as it can cause blockages.

Septic Systems

Septic Systems

Septic system postcard

Septic system owners need to regularly inspect and maintain their septic system (including repairs and replacements as their septic system ages). If septic systems are not properly maintained, they no longer receive their benefits. Instead, they can harm groundwater and pollute lakes, streams, and beaches. They can even cause sewage to surface in your yard or back up into your house. To prevent this, a septic system owner also needs to operate their system properly, such as throwing all food waste into the compost or trash can instead of tossing it down the drain (see more at Taking care of your septic system - King County).

For Additional Septic Information
Visit the King County Sewer System page, On-site Sewage System (OSS) Program - King County.

3 Steps to Lengthen the Life of Your Septic System

  1. Pump Your Septic Tank
    1. Septic Tanks are typically pumped every 3 to 5 years, depending on water use. Generally, septic tanks accommodating larger households will need to be pumped more frequently.
  2. Check for Septic System Failure
    1. Call your septic system professional if you experience any of these indicators of septic system failure:
      1. Odor
      2. Wet spots or standing water near the septic tank or drain field
      3. Backups in toilets, drains, or sinks
      4. Bathtubs, showers, and sinks drain very slowly
  3. Regularly Inspect Your System
    1. Contact a certified septic system professional to inspect and monitor your system with the following recommended frequency: 
      1. Gravity systems: Every three years
      2. Pressure distribution systems: Annually
      3. A proprietary system such as an aerobic treatment unit (ATU), membrane bioreactor
      4. (MBR), drip irrigation, and other products:
      5. Annually, or more often if required by the manufacturer
      6. Mound or sand filter systems: Annually

Find a Certified Septic System Professional

Visit the King County Site to search for certified septic system professionals: King County list of on-site sewage system professionals. 

Business Responsibilities

Fats Oil's and Grease (FOG)FOG poster

FOG solidifies and builds up over time to cause blockages. These blockages cause backups and overflows of raw sewage that can enter homes, businesses, and the environment. This can lead to human contact with disease-causing organisms, environmental damage, increased maintenance costs, and higher wastewater utility rates.

It is unlawful to discharge any of the following in the wastewater system: any water or waste which contains greater than 100 parts per million by weight of fat, oil, or grease; any flammable or explosive liquid, solid, or gas; any solid or viscous substances capable of obstructing the flow of sewers; any waste containing toxic or corrosive substances.

FOG comes from many sources. Below are some examples: 

  • Meat
  • Lard/cooking oil
  • Shortening/butter & margarine
  • Any food scraps
  • Dairy products
  • Salad dressings
  • Mayonnaise

Maintain your Grease Interceptor

An interceptor needs proper maintenance to operate efficiently. A poorly functioning or improperly maintained grease interceptor will allow FOG to bypass and enter sewer lines. Not cleaning the interceptor frequently can cause private drain line blockages, back-ups, foul odors, and loss of business. Even worse, a FOG obstruction in the City sewer line can cause a sewage overflow into the environment or other buildings. 

Clean your grease interceptor regularly to ensure that grease accumulation does not cause the interceptor to operate poorly and allow FOG to flow to the sewer. Most interceptors need to be cleaned when they become 25 percent full of FOG and solids. Routine cleaning will prevent sewer line plugging between the establishment and the sanitary sewer system. If the line plugs, the sewer line may back into the establishment, and the business will need someone to unplug it. Please contact your local vendor for emergency maintenance.