One of the most major causes of corrosion are abnormal pH scales in your local water that is running through your piping. The pH scales ranges from zero (extremely high acidity) to 14 (extremely high alkalinity); the middle of the scale, 7, is the neutral point. In copper piping low pH is acidic, and will eat away at your pipes slowly, where as a pH more than 8 forms a thin layer of copper oxide is formed on the walls of the piping, in turn this is also a protective barrier for your pipes. Even a single digit change in pH can hold massive changes to your acidity, because a single digit is a tenfold change in acidity. Normal rain has an acidity of 5.6 due to the carbon dioxide picked up in the atmosphere, acid rain has a pH of 3.6, and is 100 times the acidity of normal rain.
Oxygenation and Water
Along with pH, there is oxygen levels in the water. Most domestic water systems are in an “open” style, and is always being replenished with fresh oxygenated water. Dissolved air in water consists of abut 30% oxygen and the rest is mostly nitrogen, which is not corrosive. Oxygen degrades metals through a chemical process known as oxidation. The result is actually something I am sure you have seen, metal is converted to an oxide that is also known as rust. As the pipe corrodes, the impurities are deposited in the water lines, causing encrustation and buildup of minerals. While oxygen content decreases under higher water temperature and higher pressure, it is these higher temperatures and higher pressure conditions that speed up the oxidization process. Corrosion seems to be a lot more pronounced in hot water lines. Water that is moving faster than 4 feet a second tend to cause corrosion, along with abrupt changes in direction of the pipe.
Metals that are not similar in composition start to undergo a corrosion called galvanic corrosion when they are joined together. While touching, conflicting metals start to give up electrons. Basically, at the point of contact (pipes threaded together) the metal that is giving up electrons will dissolve over time. The most common occurrence of this is when galvanized pipe and copper pipes are connected; copper pipes touch steel studs, or steel pipe hangers. Contrary to what many people thing, the effects of galvanic corrosion are limited to the immediate area of contact. The use of dielectric fittings helps stop the problem but they do not repair the resulting thin walled and damaged pipe.
Now even though your pipes may have already been corroded, you can still repair them in several ways. The cause of corrosion in your pipes needs to be determined, items like water chemistry vary from one geographic region or from one water source to the next. The design of piping systems varies from building to building. Water velocity, water temperature, and even the metallurgy of the piping needs to be figured out. The more traditional methods of repair are as follows:
- Chemical flushing of the system
- spot repairing and replacement
- redesigning your hot water recirculation system to keep your water velocity below 4 feet a second for temperatures up to 140 degrees F, if above 140 F flow maximums are recommended to not go past 3 feet per second.
- Remove abrupt changes in piping direction.
- De-burr all tube ends before joining
- ensure all proper soldering joints
- ensure no dissimilar metals are used or make sure they are isolated
- spot repair leaks using gear clamps or other temporary devices
- use a water treatment system to adjust water quality and pH levels
- a drastic measure is to repipe the whole building or part that is corroded.
Aluminum and Plastics
A great pipe that we at Bryan Hose and Gaskets recommend to you, is a product that we carry. Aluminum piping is an extruded product that is widely used for all types of fabrication, where light weight and corrosion resistance is a priority. The main reason aluminum piping is recommended by us, is when it comes to water corrosion aluminum (like copper piping) forms an oxide layer immediately, and when the layer becomes damaged it repairs itself almost immediately. Fit to withstand pH levels from 4 to 9, its perfect for house tap water and other water lines. Other than aluminum, we can offer you a plastic based piping that is resistant to water for obvious reasons, with plastic you will not have to worry about galvanic corrosion or water corrosion. Thick PVC offers a rigid factor very similar to metal piping, and is much easier to repair or replace.
All of these products are carried by us at Bryan Hose, so give us a call and figure out which product is best for you!