City Water

Seattle Water Quality Analysis

7 min read

Seattle provides roughly 1.5 million people with drinking water.

It’s impossible to remove 100 percent of contaminants 100 percent of the time, but Seattle sure is doing their darndest to try.

Depending on who you talk to, they’re either doing an exceptional job or a decent job.

Are you ready for the cold, hard facts?

It’s time to get the unfiltered truth about the Emerald City’s water quality.

Let’s jump in!

Who Regulates Seattle’s Drinking Water?

Several federal, state and local agencies work together to keep Seattle’s tap water safe, including:

  • The Environmental Protection Agency (EPA) and the Washington State Board of Health regulate contaminants in public water systems. 
  • The Food and Drug Administration (FDA) and Washington State Department of Agriculture regulates bottled water.
  • The Department of Health Office of Drinking Water conducts Washington’s Source Water Assessment Program. 
  • The Habitat Conservation Plan and Wildland Fire Crew protect the area’s pristine watersheds. 
  • Seattle Public Utility (SPU) is in charge of treating, monitoring and testing the city’s treatment plants and distribution systems.

Here’s what Seattle Public Utility found in their latest water quality report:

Seattle Public Utility’s Annual Water Quality Report

Every year, the EPA requires Seattle Public Utility (SPU) to publish an annual Drinking Water Quality Report.

According to the latest report, SPU claims that Seattle’s water is among the best in the nation for purity and taste. 

In 2020, it met or exceeded all state and federal guidelines for water quality. 

SPU’s report covered more than 200 compounds, including many unregulated contaminants like per- and polyfluoroalkyl substances (PFAS). 

Seattle’s watersheds show no signs of PFAS, but very low levels have been detected in one of Seattle’s back-up wells. However, these levels were well below the EPA’s testing threshold.

Their lead and copper monitoring results also found no detectable lead in the city’s source water. 

With that said, lead and copper can still leach into water after treatment, but more on that later…

For now, let’s see what the Environmental Working Group has to say about Seattle’s water:

Environmental Working Group’s Water Quality Report 

The Environmental Working Group (EWG) is a non-profit organization that publishes their own water quality reports.

They use data from the Washington State Department of Health and the US EPA Enforcement and Compliance History database (ECHO).

Overall, the EWG’s health standards are a lot stricter than the federal government’s. 

In their latest report, the EWG found 8 cancer-causing contaminants above healthy limits, including:

  • Bromochloroacetic acid: 17x EWG HEALTH GUIDELINES
  • Bromodichloromethane: 38x EWG HEALTH GUIDELINES
  • Chloroform: 79x EWG HEALTH GUIDELINES
  • Hexavalent chromium: 5.8x EWG HEALTH GUIDELINES
  • Dichloroacetic acid: 74x EWG HEALTH GUIDELINES
  • Haloacetic acids: 350x EWG HEALTH GUIDELINES
  • Total trihalomethanes: 226x EWG HEALTH GUIDELINES
  • Trichloroacetic acid: 191x EWG HEALTH GUIDELINES

DID YOU KNOW?

Across the country, levels of disinfection by-products (DBPs), like haloacetic acids and trihalomethanes, are highest between the months of May and August. Apparently, DBPs love the summer just as much as you do!

Lab tests show that these substances can have negative side effects on living organisms, although more human studies are needed. 

So which report is the most accurate? SPU’s or the EWG’s? The jury is still out on that one! 

If you want to play it safe, you can always install an in-home water filter, but more on that in a sec…

Next up, let’s take a look at where Seattle gets its water:

Where Does Seattle Get Its Water?

Seattle’s water starts as snow that collects in mountain watersheds. 

When it melts in the spring and summer, it provides a steady supply of fresh water. 

The water begins in the Cascade Mountains and travels through more than 1,800 miles of pipes from forest to faucet.

Seattle manages two large watersheds: the Cedar River and the South Fork Tolt River watersheds. 

63 percent of the city’s water comes from Cedar River and 37 percent from the Tolt. 

If you live south of Green Lake in Seattle, your water most likely comes from Cedar River, while areas north of Green Lake receive Tolt water. 

how safe is your local tap water?

There are many ways to test the quality of your tap water. Some cost money, like having your water professionally tested, but you can also check your community's latest test results by simply entering your zip code below.

Treating Seattle’s Drinking Water

Seattle treats its drinking water in two state-of-the-art treatment plants: the Cedar Water Treatment Facility and the Tolt Water Treatment Facility

The Cedar facility produces up to 180 million gallons of water per day from the Cedar River and Lake Youngs. 

For the most part, both facilities use the same treatment process, with a two main differences: 

  • The Cedar facility uses ultraviolet (UV) light disinfection, whereas the Tolt facility does not. 
  • Water from the Cedar Water Treatment Facility is so clean that it does not require filtration as part of treatment. It is one of only four facilities in the entire country that meets this standard. 

Here’s a closer look at Seattle’s treatment process in action:

  • Ozone Generation & Injection: Ozone is a disinfectant that kills algae blooms and is great for eliminating unpleasant tastes and odors. 
  • Conditioning & Filtration: Conditioning compounds are added to the water to give it a better consistency for filtering. It is then filtered through a bed of granular media to trap contaminants.
  • Ultraviolet Light Disinfection: UV reactors kill Cryptosporidium, Giardia and other pathogens with UV light. 
  • pH Adjustment: The water’s acidity level is adjusted to make it less corrosive to lead and copper plumbing. 
  • Fluoridation: Fluoride is added to the water to prevent tooth decay. 
  • Chlorination: A small amount of chlorine is added to chemically disinfect and kill any remaining pathogens. 

Following treatment, the water is stored in clear-water tanks before traveling through distribution pipes to homes and businesses across the city. 

Testing and Monitoring Seattle’s Water

Seattle Public Utility tests water sample between 10 and 100 times per day. 

More than 90 water sampling stations are spread throughout the city.

At the same time, the Department of Health (DOH) monitors all source water in rivers, lakes and reservoirs as part of Washington’s Source Water Assessment Program. 

Water quality in Lake Youngs is especially vulnerable to algae growth, so the DOH watches like a hawk in spring and summer. 

Next up, let’s take a closer look at the many contaminants that threaten Seattle’s water supply:

Contaminants Threatening Seattle’s Water Supply

As water travels through rivers, lakes and streams, it has plenty of chances to pick up pollutants. 

Many are man-made chemicals, but others are naturally occurring minerals and metals in the rocks and soil. 

Common drinking water contaminants include:

  • Viruses, bacteria and parasites from septic tanks, livestock operations and sewage plants
  • Organic contaminants like salts and metals
  • Inorganic contaminants like disinfection byproducts (DBPs) from chlorine
  • Pesticides and herbicides from agriculture and residential uses
  • Salts, metals and other byproducts from industrial waste, mining, farming, urban stormwater and oil and gas production
  • Radioactive contaminants from oil, gas and mining operations, as well as some that occur naturally in the rocks and soil

Be safe and recognize your risks! 

Some people are more vulnerable to side effects from contaminated water, especially people with immune disorders, the elderly and young children. 

Fortunately, Seattle’s watersheds are closed to public access and are free of agricultural, industrial and recreational activities. 

Reducing the Risk of Lead Exposure

Lead can cause side effects like abdominal pain, fatigue, headaches and even brain and kidney damage. 

Immediately after treatment, Seattle’s water is 99.9% lead-free. 

Seattle’s source water in lakes and rivers are also free of lead.

The problem is that old lead service lines and lead pipes in homes are still in use throughout the city. 

Lead service lines were common until 1951 and lead pipes were installed in homes through 1986.

Over time, they can corrode and leach lead into your tap water. 

It’s very important to be aware of when your pipes were installed.

If you have an older home, you should have your water professionally tested and contact a plumber to check out your plumbing.

In the meantime, you can always install an NSF-certified filter that removes lead. 

Here’s a few more tips to reduce the risk of lead exposure:

  • Run your water for five minutes if it hasn’t been used in a few hours. 
  • Only use cold water for drinking and cooking.
  • Replace old faucets and fixtures with lead-free ones.
  • Remove and clean faucet screens (aerators). 

Although you may or may not have to worry about lead, everyone has to worry about DBPs...

Disinfection by-products (DBPs) are produced when disinfectants like chlorine mix with organic matter in drinking water. Unfortunately, chlorine is the best way to keep large public water supplies safe. The good news is that you can remove up to 99.9% of chlorine and DBPs by installing and in-home water filter. That way you can get the best of both worlds!

Seattle Water Quality Analysis Microbes

Disinfection Byproducts In Seattle’s Drinking Water

Seattle’s water treatment plants use chlorine to chemically disinfect their water. 

When chlorine mixes with organic matter in water, it releases toxic compounds called disinfection byproducts (DBPs). 

DBPs can have harmful health effects, including cancer and problems with the liver, kidneys and central nervous system. 

Unfortunately, DBPs are a necessary evil…

That’s because chlorine and similar chemicals are the only way to effectively disinfect large volumes of water. 

In order to cut down on DBPs, Seattle also uses ultraviolet radiation and ozone to disinfect their water. 

They also minimize the amount of DBPs by the following methods:

  • Reduce organic substances in water before chlorine treatment.
  • Shorten contact time with chlorine in the distribution system. 
  • Increase the turnover rate of water in storage tanks.
  • Change the locations where they add chlorine.

At home, you can take matters into your own hands by installing a UV system or reverse osmosis (RO) filter...

Should Seattle Residents Use In-Home Water Filters?

Even if the city does everything perfectly, you can still be exposed to contaminants like lead and DBPs. 

The best way to protect your family is to install an RO filtration system.

They combine sediment filters, activated carbon filters, ion exchange resins, RO membranes and polishing filters to remove lead, DBPs, bacteria and up to 99.9% of all harmful contaminants.  

High-end RO systems even use remineralization to add the perfect amount of healthy minerals back into the water. 

Cloud Water Filters also use built-in software to monitor your water quality 24/7. 

You’ll never have to worry about water quality again!

Click here to learn more.

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