What are the disadvantages of GI pipes?

GI pipes (Galvanized Iron Pipe) are pipes made by hot-dip galvanizing on the surface of carbon steel. Although they are widely used in water supply, fire protection, construction and other fields, they have the following main disadvantages:

1. Limited corrosion resistance

Zinc layer is easy to wear out:
The galvanized layer will gradually oxidize (white rust, red rust) over time, especially in humid, acidic or high-salt environments.

After the galvanized layer is damaged, the internal carbon steel will corrode rapidly, causing the pipe to leak. Especially in acidic or high-temperature environments, the corrosion rate is faster, which will affect the service life of the pipe.

Not suitable for highly corrosive media:
When transporting acidic, alkaline or chlorinated water (such as swimming pool water, chemical fluids), the service life is significantly shortened.
Comparison: Stainless steel pipes or PVC pipes perform better in corrosive environments.

2. Easy to scale and clog

Zinc layer falls off:
After long-term use of galvanized iron water pipes, the zinc layer may peel off and form sediments, clogging the pipe.

Scale accumulation: In hard water environment, the inner wall of galvanized iron water pipes is prone to scale, reducing water flow and increasing maintenance costs. In addition, the scale layer is easy to hide harmful substances such as bacteria and viruses, thus affecting water quality. Application restrictions: Not recommended for drinking water systems (modern standards often use PPR or stainless steel pipes). 

3. Difficult welding and processing 

Toxicity of zinc layer: 

When welding or cutting, the zinc layer evaporates to produce toxic zinc oxide fumes. 

Special treatment required: 

The galvanized layer needs to be polished and removed before welding, otherwise it is easy to produce pores and cracks. 

Alternatives: Seamless steel pipes (such as ASTM A106) or plastic-coated steel pipes are recommended for occasions where welding is required. 

4. Heavy weight and high installation cost 

Heavier than plastic pipes: 

Under the same size, the weight of GI pipes is 3 to 5 times that of PVC pipes, which increases the difficulty of transportation and installation. 

Complex threaded connection: 

Relying on threaded or flange connections, the installation efficiency is lower than that of plastic pipes connected by hot melt. 

Economical: The initial cost is low, but the long-term maintenance cost may exceed that of plastic or stainless steel pipes.

5. Hygiene issues (drinking water field)

Zinc contamination risk: Old galvanized iron water pipes may release zinc ions, causing water quality to smell.

Bacterial growth: The rough surface after the inner wall is corroded is easy to breed bacteria.
Modern alternative: Drinking water systems generally use 304 stainless steel pipes, CPVC or PPR pipes.

6. Applicable temperature restrictions

High temperature deformation: Long-term exposure to an environment >60°C may accelerate the aging of the zinc layer and increase the risk of deformation of the steel pipe.

Low temperature brittleness: The galvanized layer is prone to cracking at low temperatures (<0°C) and is not suitable for freezing liquid transportation.
High temperature alternative: A106 GR.B seamless steel pipe is recommended for steam or high temperature water systems.

Recommended scenarios for galvanized iron water pipes:
Can continue to be used: short-term low-pressure water supply, fire sprinkler system (non-corrosive environment).

Recommended elimination: drinking water system, chemical pipeline, high-temperature steam pipeline.

Read more: Galvanized Carbon Steel Pipe