”Nature is constantly striving to reach balance and equilibrium.  Corrosion  is the natural deterioration  of materials by chemical and physical interaction with the external environment. Man creates, and nature destroys; this is the essence of corrosion.”—Greg Reyneke.  Water Conditioning and Purification Magazine, April 2010.

Symptoms

Yellow, green, orange or blue coloring of water.  These are symptoms of metallic corrosion.

Yellow, green, orange or blue coloring of tubs, toilet bowls and tanks.  These are symptoms of metallic corrosion.

Tastes and Odors.  Corrodsion by iron, copper, and brass make bitter or metallic taste and sometimes odors.

Sediment and particulate.  Rust accumulates as reddish-brown sediment.

Leaks.  Dripping water and crustaceous deposits on the outside of pipes are signs of corrosion within.

Causes

1. High flow rates.  “When flow velocity becomes excessive, pitting is the inevitable result.” 
   
   
2. High TDS.  Over 500 ppm TDS, the potential for corrosion increases.
   
   
3. Low pH.   As pH goes below 7.0, the potential for pitting and corrosion increases.
   
   
4. High water temperature. Warm water speeds up chemical reactions and also liberates dissolved CO2, which contributes to corrosion.
   
   
5. Suspended solids can act as sandpaper inside pipes and appliances. Dissimilar metals in contact.  Galvanic action is the most significant single contributor to metallic corrosion.

7. Chlorine and Chloramine.  These common disinfectants lead to the breakdown of both metals and rubber materials. 

8. Chloride.  Chlorides are the enemy of stainless steel. 

9. Biofilm. Biofilm grows in all water systems and it encourages corrosion.

Treatment.  Treatments for corrosion, obviously, are many, since the causes are many.  Some common treatments are increasing pH, reducing chlorides (reverse osmosis), reducing chloramines and chlorine (carbon filtration), turning down the hot water heater, filtering out excessive sediment, or decreasing the demand for flow through the piping.

Main source: Water Conditioning and Purification Magazine, April 2010.