Blue water stains are due to a corrosion and are directly related to copper water lines in the home. In some instances this phenomenon manifests itself shortly after a new plumbing system is put into continuous service and then eventually goes away. Notice of this situation occurs, and concern generally arises, when it causes a slight blue or green discoloration in the water or, more commonly on surfaces that come in contact with the water such as plumbing fixtures. Electrolysis and or high acidity can contribute to staining and is often found in untreated water systems such as well water in a forested area with pine trees.
The majority of high copper level cases or blue water staining is caused by interaction between the copper tube wall and elements or compounds in the water. Fabrication of the tube is not normally found to be a factor in high copper level occurrences. This is because the smooth drawing of the tube through the blocks requires a consistent alloy structure. Tubes that may have an inclusion in the tube wall or inconsistencies in the make-up of the alloy tend to collapse, bend, or break during drawing and never get to the marketplace.
Discoloration occurs due to a fine dispersion of copper corrosion in the water conveyed by the system. Elevated copper levels may be a result of either dissolved copper, particulate copper, or both. Usually in cases where this occurs, the inside surface of the tube will be covered by a loosely adhering powdery scale or, if the water velocities in the system are high, no scale will be present. Instead there will be a general dissolution or corrosion of the copper resulting in a high sheen on the inside of the copper tube wall.
Typically stain will occur in fixtures serviced by water with low pH. It generally is characterized by elevated levels of dissolved copper in the water. However it does not usually result in high levels of particulate copper, or suspended copper corrosion products in the water.
The best way to get rid of this occurrence is to have your water tested by a reputable filter company. They will make recommendations for the best whole house filter. Usually a Calcite Filter will do the job.