Galvanized Iron Pipes

GI pipes are most often used for plumbing and construction applications in the Philippines because their zinc coating protects them from rusting very easily due to the high humidity levels that are common throughout much of the Philippines.

Locally, they are categorized by wall thickness: Schedule 40 (Standard) and Schedule 80 (Extra Heavy). They are also classified by “Class,” such as Light (Class A), Medium (Class B), and Heavy, depending on the pressure or weight they need to handle.

Generally, they last between 20 to 50 years. In a controlled environment, they lean toward 50. However, in the Philippines’ salty coastal areas or if used for hot water, the lifespan might drop toward the lower end as the zinc wears down faster.

Rust occurs when the zinc coating erodes, exposing the raw iron to moisture and oxygen. This usually happens due to age, internal mineral buildup, or “galvanic corrosion”, which occurs if your GI pipes are directly connected to copper pipes without a proper fitting.

Yes but not the ideal situation. You can do this but the acidic properties of the soil along with continually being exposed to moisture will accelerate the corrosion on the zinc surface faster than if installed above ground. If you must bury them, then normally contractors apply bituminous protection or anti-corrosive tape around the pipe to prolong its longevity in the underground environment.

Standard lengths are 6 meters. Common nominal diameters in local hardware stores range from 1/2 inch, 3/4 inch, and 1 inch for residential plumbing, up to 2 to 4 inches or more for industrial and structural applications.

For bulk project rates, look for wholesalers in Metro Manila and nearby provinces like Laguna, or industrial suppliers in Valenzuela and Quezon City who offer mill certificates for quality assurance.