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Selecting the right metal pipe is not just about cost; it is about
lifecycle engineering. The wrong choice can lead to catastrophic failures,
contamination, or exorbitant maintenance costs.
Carbon Steel (Black Steel vs. Galvanized)
Black Steel: Malleable and strong, used primarily for gas lines and fire
sprinklers. It rusts easily if not painted.
Galvanized Steel: Coated with zinc. Ideal for water supply in residential
homes. However, the zinc eventually erodes, leading to "red rust" and reduced
water pressure due to internal buildup. Avoid using galvanized pipes with
stainless steel fittings to prevent galvanic corrosion.
Stainless Steel (304 vs. 316)
304 (Food Grade): The standard for potable water and food processing. It
resists corrosion well but is vulnerable to chlorides (salt).
316 (Marine Grade): Contains 2-3% molybdenum. This makes it immune to
pitting corrosion in salty or chemical environments. Essential for coastal
desalination plants or chemical transport.
Copper
Type L (Thick wall): Used for main water lines. Highly durable and
naturally bacteriostatic (kills bacteria).
Type M (Thin wall): Used for branch lines inside walls. Cheaper but more
prone to puncture during installation.
Limitation: Copper is expensive and can be stolen for scrap value. It is
also rigid, requiring more fittings (elbows) which are potential leak
points.
Key Selection Criteria
Fluid Compatibility: Is the liquid acidic or alkaline? (e.g., PVC is bad
for hot water; CPVC is good).
Pressure Rating: Schedule 40 (standard) vs. Schedule 80 (extra heavy).
Temperature: Metal expands and contracts. Stainless steel handles thermal
cycling better than cast iron, which can crack.
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