Copper in Minnesota Drinking Water

Copper is a naturally occurring element in rock, soil, water, plants, sediment and air. This “transitional metal” is typically dissolved in water as a divalent cation (Cu+2).

What are the Health Effects of Copper in Drinking Water?

Copper is actually an essential element for living organisms because it acts as a catalyst for producing enzymes. Too much copper, however, can be damaging to health:

• Gastrointestinal distress
• Nausea and vomiting
• Long-term excess exposure associated with liver damage, kidney disease

How is Copper Regulated?

US Department of Agriculture (USDA) recommends the following:

• Maximum intake not to exceed 10 milligrams per day (mg/day) for adults
• Recommended intake for adults: 1.0 to 1.6 mg/day

The Environmental Protection Agency (EPA) has established the following limits:

• Maximum Contaminant Level Goal (MCLG): 1.3ppm
• Action Level: 1.3ppm
• Secondary Maximum (recommended to avoid metallic taste or blue-green staining): 1.0 ppm

Where Does Copper Come From?

Copper ore is widely used in copper pipe and tubing. Copper compounds also used for pesticides and algae control. Natural levels of copper in groundwater and surface water is about 4ppb (parts per billion) or less.

Drinking water may contain higher levels of dissolved copper from corrosion of copper plumbing. Level increases with corrosivity of the water and contact time with the plumbing.

Copper may also be discharged from wastewater treatment plants as it does not break down in the environment.

Copper Plumbing Corrosion:

Blue-green stains on fixtures are often an indicator of corrosion in copper piping/tubing. Copper corrosion may be have several causes that are water related:

Pitting: Pinhole leaks and surface pitting are common, especially in cold water with:

• pH of 7.0 to 7.7
• Dissolved Oxygen exceeding 3 parts per million (ppm)
• Carbon Dioxide of 25ppm or more
• Sulfate-to-Chloride ratio greater than 3-to-1
• Water containing Iron, Manganese or Aluminum

Erosion: More common with:

• Recirculating hot water (140°F/60°C or more)
• High flow water velocities
• Excess pipe burrs and solder globules disrupting laminar flow

Recommended Water Treatment Options for Copper

Point-of-entry (POE)

• pH control with a Neutralizing Whole-House Filter
• Film-Creating Compounds (Food-Grade Polyphosphates)
• Reverse Osmosis