Corrosion of steel is strongly affected by the amount of oxygen in the water and the temperature of the water. The effects of oxygen and temperature on low-carbon steel pipes with water flow are indicated in the diagram below:

• 1 mm = 0.03937 in
• T(^oF) = [T(^oC)](9/5) + 32

The diagram indicates clearly how important it is to avoid continuously fresh water supply in higher temperature systems - like heating systems or similar - where the piping is made of carbon steel.