Cedar Mill Water Hardness & Quality Report (2026)

Tualatin Valley Water District provides water to over 50,000 customers in Cedar Mill, Oregon, and surrounding areas in Washington County. The primary water source comes from the Portland Water Bureau's Bull Run Watershed, which is treated at the Bull Run Water Treatment Plant. This supply is supplemented by the Joint Water Commission (JWC), drawing from the South Fork Clackamas River and treated at the Clackamas River Water Treatment Plant. TVWD blends these sources and distributes the water through its network, maintaining disinfection and adjusting pH without additional softening.

The Bull Run Watershed is located in the Mount Hood National Forest, underlain by Tertiary volcanic rocks including the Columbia River Basalt Group and Otter Creek Formation volcanics. The Clackamas River source also features similar Cascade geology. These igneous and sedimentary rocks are low in soluble minerals like calcium and magnesium, leading to naturally soft water. The absence of extensive limestone or dolomite formations means minimal mineral leaching into the water supply.

Because the water is naturally soft, Cedar Mill residents experience very little limescale buildup. This spares appliances like water heaters and dishwashers from damage and allows laundry detergents to work efficiently. While soft water is generally beneficial for appliances, the low mineral content can sometimes pose a risk of corrosion to pipes and fixtures. TVWD adjusts the water's pH to help control this, and homeowners might consider phosphate inhibitors if pitting is observed. Routine cleaning is usually sufficient for any minor soap scum residue. The Tualatin Valley Water District provides water to over 50,000 customers in Cedar Mill, Oregon, and surrounding areas in Washington County. The primary water source comes from the Portland Water Bureau's Bull Run Watershed, which is treated at the Bull Run Water Treatment Plant. This supply is supplemented by the Joint Water Commission (JWC), drawing from the South Fork Clackamas River and treated at the Clackamas River Water Treatment Plant. TVWD blends these sources and distributes the water through its network, maintaining disinfection and adjusting pH without additional softening.

The Bull Run Watershed is located in the Mount Hood National Forest, underlain by Tertiary volcanic rocks including the Columbia River Basalt Group and Otter Creek Formation volcanics. The Clackamas River source also features similar Cascade geology. These igneous and sedimentary rocks are low in soluble minerals like calcium and magnesium, leading to naturally soft water. The absence of extensive limestone or dolomite formations means minimal mineral leaching into the water supply.

Because the water is naturally soft, Cedar Mill residents experience very little limescale buildup. This spares appliances like water heaters and dishwashers from damage and allows laundry detergents to work efficiently. While soft water is generally beneficial for appliances, the low mineral content can sometimes pose a risk of corrosion to pipes and fixtures. TVWD adjusts the water's pH to help control this, and homeowners might consider phosphate inhibitors if pitting is observed. Routine cleaning is usually sufficient for any minor soap scum.