Can Black Steel Pipe be Used for Water?

Can Black Steel Pipe be Used for Water Transportation?

Black steel pipe can be used for water transport, but it's generally not a direct, final solution, especially not ideal for drinking water transport. Its use requires specific prerequisites and application scenarios.

The following provides a detailed analysis of the water transport applications, advantages, disadvantages, and precautions of black steel pipe:

Common Uses of Black Steel Pipe for Water Transport:

1. Non-potable/industrial water

This is the most common use for black steel pipe. For example:

Fire sprinkler systems: Fire sprinkler pipes within buildings. These pipes are typically painted with red fire retardant paint to meet fire regulations and prevent rust.

Industrial circulating water: Circulating water systems used for cooling or process flow in factories.

2. Municipal water supply mains

In some large-scale municipal water supply projects, professionally treated internal and external corrosion resistant black steel pipe is used. The base material is black steel pipe, but it has been treated with a high-grade corrosion resistant treatment (triple polyethylene).

3. Irrigation water: Main pipes for agricultural irrigation.
4. Temporary water supply: Temporary water supply pipes at construction sites and other locations.

The Main Issues with Using Black Steel Pipes for Water Transportation:

The core reason why bare black steel pipes cannot be used directly for water transportation, especially drinking water, is:

1. Black steel pipes are extremely susceptible to rust and corrosion.

Internal rust: Flowing water gradually rusts the inner wall of the steel pipe. The rust flakes off, contaminating the water, causing it to turn yellow and develop an unpleasant odor.
External rust: In humid environments, rust on the outer wall of black steel pipes can weaken the pipe wall, shortening its lifespan and ultimately leading to perforations and leaks.

2. Bacterial growth

The rough rust on the inner wall of black steel pipes easily attracts impurities from the water, creating a breeding ground for microorganisms (such as iron bacteria), affecting water quality and hygiene.

3. Increased water flow resistance: Rusted, roughened inner walls increase water flow resistance and increase pump energy consumption.
4. Scaling: Minerals in the water easily deposit and form scale on the rusted surface, further reducing the pipe diameter, affecting flow, and even causing blockages.

Correct Treatment and Use of Black Steel Pipes:

If you decide to use black steel pipes for water transportation, they must undergo strict post-treatment depending on the intended use:

1. Firefighting Water, Industrial Water

Recommended Treatment:
• Exterior: Spray with anti-rust paint.
• Interior: For less demanding systems, no treatment is required (but this will shorten the lifespan); for demanding systems, interior corrosion protection can be applied.

2. Municipal Water Supply, Drinking Water

Professional internal and external corrosion protection is required:
• Internal: Cement mortar lining or epoxy resin coating. This is standard for large water pipes and effectively prevents rust and ensures water quality.
• External: 3PE (three-layer polyethylene) or epoxy coal tar coatings are used to prevent soil corrosion.

3. Temporary Water Use

Temporary use is acceptable, but please be aware that rust can occur quickly and the pipe is not suitable for drinking water.

What are some alternatives for water pipes?

For direct, long-term water supply (especially drinking water), there are now many better options than bare black steel pipe:

1. Galvanized Steel Pipe
A layer of zinc is hot-dip coated on the surface of black steel pipe, significantly improving its rust resistance.
Disadvantages: The zinc coating may flake off after long-term use, posing a risk of corrosion. Furthermore, zinc ions are now considered to have potential health effects, making their use unrecommended for new drinking water systems.

2. Plastic Pipe
PE Pipe (Polyethylene Pipe): The preferred choice for buried water supply pipes, offering corrosion resistance, excellent flexibility, and a long service life.
PPR Pipe (Polypropylene Random Copolymer Pipe): The mainstream choice for indoor drinking water pipes, offering non-toxicity, heat resistance, and resistance to scaling.

3. Composite Pipe
Steel-Plastic Composite Pipe: Combining the strength of steel with the corrosion resistance of plastic, it is the ideal choice for high-performance water supply systems.
Stainless Steel Pipe: Excellent corrosion resistance and optimal sanitation, but with a higher cost. It is primarily used in high-end buildings or applications with extremely high water quality requirements, such as food processing, medical equipment, and the chemical industry.

Conclusion:

Black steel pipe can be used as a base material for water pipes, but it should never be used directly. If you need to lay water pipes, especially for household drinking water, you should prioritize PPR or PE pipes. For large-scale projects, professionally treated steel pipes are a viable option, but bare black steel pipes should be avoided due to their significant corrosion risk.

Read more: Advantages and Disadvantages of Black Steel Pipe or API 5L Seamless Line Pipe