Blue-green colored water or stains on clothes, fixtures, sinks, tubs, water-using appliances, and toilets are an indication of the presence of copper in the water supply. Typically, this is caused by the corrosion of copper pipes by low-pH water (acidic water). 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.