According to some estimates, corrosion costs the United States more than $1 billion every year. Besides actual piping failure and pinhole leaks, copper corrosion leaves blue stains on sinks, tubs, fixtures, laundry and hair.
Corrosion can also make the water unfit for drinking. Copper can be toxic and water containing levels over 1.0 mg/L should not be used for drinking.
The main causes of copper corrosion are:
Low pH (acid water less than 7.0) or high pH (alkaline water greater than 8.5)
High levels of dissolved oxygen
High levels of salts dissolved in the water (total dissolved solids)
Corrosion-causing bacteria such as sulfate or iron bacteria
Electrochemical causes, such as improper grounding of electrical appliances to the copper piping, and/or lightening strikes through utility poles grounding wires
High velocity of water, relative to size of piping, causing hydraulic wear on the piping, sometimes found in circulating hot water systems using pumps
Sand, sediment or other grit in the water causing hydraulic wear on the piping
Improper installation of copper piping, and in particular the failure to properly de-burr or ream the ends of the pipe and/or the installer using excessive acid flux when soldering the pipes.
Once corrosion starts in a copper piping system, electrons can begin to flow between the corrosion sites in the pipe, causing the copper to dissolve into the water. Since water contains oxygen, the copper ions rust or oxidize, to blue color. This same process happens in galvanized iron piping, causing rust stains and red water.
What can be done?
1. Identify the source and severity of the problem by inspection of the piping system and getting an accurate water analysis especially if you are on well water.
2. Check to see if there are unnecessary electrical appliances or wiring connected to the piping and if the piping system is properly grounded to an earth ground. Verify to make sure that there is electrical continuity through out the piping system. For instance, the copper piping should not be separated electrically by plastic water filters, sections of plastic pipe, plastic water softener bypass valves etc. Jumper cables can be installed around these items.
3. Check for pH and see if the water is corrosive
4. Cut out sections of the copper piping, cut in half and inspect to the type of corrosion present and for signs of poor workmanship by the installers. Replace copper pipe if necessary.
5. Install a calcite neutralizer tank, or a soda ash feeder to raise the pH to 7.2 to 8.0 to correct for low pH and increase the alkalinity in the water.
6. Install a phosphate feeder before the copper piping. Phosphate will coat the piping and reduce or slow down the corrosion effects, by coating the interior surfaces of the piping with phosphate and causing an insulation surface to be built up.
7. In case of high total dissolved solids (over 1000 ppm) install a whole house reverse osmosis system, followed by a calcite neutralizer.
8. If your water has bacteria and/or sulfur odors, install a chlorinator or ozone system to disinfect the water before it enters the home.
If your water is supplied to you by a municipal utility then the first place to start is by calling your water utility and reporting the problem. If this is an isolated case and none of your neighbors are having a corrosion problem you should suspect that the cause is either improper grounding, stray currents, or improper installation of the copper pipe.
If you take your water from a private well then the first task you should do is to get an accurate water analysis. The water analysis should be for pH, total hardness, alkalinity, total dissolved solids, iron, manganese, nitrate, chloride, sulfate, and copper.
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