Deciphering Blue Staining in Plumbing: Origins and Solutions

Understanding and Addressing Blue Staining in Plumbing Fixtures and Appliances

Blue or green discoloration in plumbing fixtures and appliances, particularly sinks, bathtubs, dishwashers and coffeemakers represents a prevalent concern for many homeowners. This article aims to provide clarity on the origins of this staining, methods for its identification, and effective solutions to mitigate its impact.

Here are some examples of blue / green water problems.

Blue tinted water in tub 
Blue tinted water in bathtub
Copper blue stains in Keurig water reservoir
Copper blue stains in Keurig water reservoir
Copper Pipe Corrosion and Pin Hole Leak Caused by Aggressive Water
Copper Pipe Corrosion and Pin Hole Leak Caused by Aggressive Water

Origins of Blue Staining in Plumbing

The primary source of blue or green staining in plumbing fixtures is the corrosion or dissolving of copper pipes and fittings. Such corrosion is predominantly driven by water that exhibits a high degree of acidity. Specifically, when water has a pH level below 7 or a Total Dissolved Solids (TDS) measure below 100 mg/l. Water that has a low pH or turbidity is termed "aggressive water." This aggressive water, in its interaction with copper pipes, valves and fittings, leads to the manifestation of blue or green stains.

The situation is further exacerbated when the water contains elevated levels of dissolved oxygen, carbon dioxide, and other gases. The aggressive nature of the water facilitates the erosion of minute quantities of metal from the pipes, valves and fittings. This metal dissolution not only discolors the water but also, over prolonged exposure, leads to the formation of stains on fixture and appliance surfaces. If not addressed, aggressive water even leads to failure as evidenced by leaks and damage to the home.

Symptoms of aggressive water, and by extension copper corrosion, include blue or green water discoloration, the appearance of greenish soap scum, blue and green stains on tubs, showers and appliances and a distinct metallic or medicinal taste in the water.

Addressing Blue Staining from Aggressive Water

While multiple solutions exist for addressing copper staining, the most effective approach targets the root cause – aggressive water. Viable solutions include:

  1. Calcium Media Filter Installation: Introducing a filter filled with calcium media can neutralize aggressive water. As the water travels through this filter, the calcium is dissolved which increases both the pH and the TDS, which curtails the water's propensity to dissolve metallic elements. However, one must be cognizant that while this method addresses the staining issue, it might simultaneously elevate water hardness, presenting another set of challenges including the possibility of having to add a water softener.
  2. Utilization of Cascadian PolyHalt®: An alternative to the calcium-based media approach is the employment of Cascadian PolyHalt®. PolyHalt® effectively shields plumbing from the deleterious effects of corrosion, along with other minerals like silica, iron, and manganese. PolyHalt® accomplishes this by creating a protective layer between the water and metallic elements, preventing any corrosive interactions. Importantly, it addresses the issue of water acidity and low TDS without introducing hardness minerals, offering a simpler yet comprehensive solution.


In conclusion, understanding the reasons behind blue staining in plumbing pipes, valves, fittings, fixtures and appliances is crucial for effective mitigation. Through informed measures, one can ensure the longevity of plumbing infrastructure while maintaining water quality. Learn more about water quality issues here. Try our very effective Filter Finder Quiz to find your perfect water treatment solution, pure and simple.