Blue-green stains on clothes, fixtures, sinks, tubs, water-using appliances, and toilets are an indication that you may have low pH water, or acidic water. This blue-green color is caused by acid-corroded copper in your pipes, which also makes your water unsuitable for drinking. Problems with pH may be caused by acid rainfall, naturally low pH water, poor plumbing practices, improper electrical grounding, and more. A neutralizing filter or soda ash injection can be used to balance the pH of the water. 

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Treatment Methods: neutralizing filter, soda ash injection