It is very important to choose the material for the water and electricity pipeline in our family decoration. The quality of the material will directly affect its use in the future.
For example, the water pipe throughout the toilet, kitchen, and other water areas, once the wrong choice, post-maintenance, and replacement will be a big project.
Moreover, the quality of water pipe directly affects the water quality, related to people’s health problems, so the choice of water pipe must not be ignored.
Since August 1, the new national standard requires indoor water supply pipes to use stainless steel pipe and copper pipe, but what is the difference between the two pipes?
Copper Pipes VS Stainless Steel Pipes
In fact, stainless steel pipe and copper pipe are both high-quality water supply metal pipes, but because the price of copper pipe is relatively cheap, the development time is also relatively long, so the copper pipe as a water supply pipe is more common.
Copper pipes
Copper pipes are a kind of purplish red shiny metal, slightly hard, it is pressed, and drawn seamless pipe.
Copper pipe has the characteristics of good electrical conductivity, thermal conductivity, electrical accessories of electronic products, and the main material of heat dissipation accessories, and become the first choice of modern contractors in all residential commercial housing water pipes, heating, refrigeration pipeline installation.
Copper pipe has strong corrosion resistance, is not easy to oxidize, not easy to react with some liquid substances, and is easy to bend shape.
Stainless Steel Pipes
Stainless steel pipe is a hollow strip of circular steel, widely used in petroleum, chemical, medical, food, light industry, mechanical instrument, and other industrial pipeline and mechanical structure parts.
Also commonly used as furniture kitchenware.
1. Physical Properties
- Tensile strength: taking SS 304 pipes as an example, its tensile strength is 530 ~ 750Mpa, twice that of galvanized pipe and three times that of copper pipe. Therefore, SS pipe wall thickness than the copper pipe can be thinner (0.6mm), in line with the national industrial policy of material saving, but also the guarantee of strength, and can achieve the purpose of reducing the bearing capacity of the building.
In contrast, copper pipes are more likely to leak under the influence of external forces.
- Thermal conductivity: the thermal conductivity of a stainless steel pipe is 15 W/m℃(100℃), which is 1/4 of the carbon steel pipe, and 1/23 of the copper pipe. Because of its good thermal insulation performance, stainless steel pipe is especially suitable for hot water transportation, whether the thickness of the insulation layer or the construction of thermal insulation structure, maintenance costs, etc., SS pipe has a better economy.
And copper pipe needs a professional insulation layer, otherwise heat energy waste is too big.
- Thermal expansion coefficient: the average thermal expansion coefficient of a stainless steel pipe is 0.017mm/ (m℃), which is close to copper pipes.
SS Pipes VS Copper Pipes in Physical Properties
| Content | SS pipes | Copper Pipes | Note |
|---|---|---|---|
| Tensile Strength Mpa | 530~750 | 200 | Stainless steel pipe strength is 3 times of copper pipe, suitable for high-rise water supply |
| Coefficient of thermal expansion 10-6/ °C(0-100 °C) | 17 | 17.6 | There is little difference between the two, but the stainless steel tube has the characteristics of slow expansion and contraction |
| Thermal conductivity W/M°C(100°C) | 15 | 340 | The thermal conductivity of stainless steel tube is 1/23 of copper tube, especially suitable for hot water transportation, and copper tube needs professional insulation layer, otherwise the heat energy waste is too big |
| Tube Diameter mm | 12.7~400 | 12.7~300 | almost the same |
| Pipe connection | Socket argon arc welding, jam welding, jam-on, ring crush, grooved connection | jam-on, hard-solder | Stainless steel pipe socket argon-arc welding type can withstand pressure above 2.5Mpa |
| Retrievability | Can be 100% recycled | Can be 100% recycled | Metal pipe can be recycled, in line with the national energy saving policy |
| Flammability | non-ignitable | non-ignitable |
SS Pipe VS Copper Pipe in Flow Rate (L/Min)
| Pipes | DN | ||||||
|---|---|---|---|---|---|---|---|
| Pipes | 15 | 20 | 25 | 32 | 40 | 50 | 65 |
| 1/2 | 3/4 | 1 | 11/4 | 11/2 | 2 | 21/2 | |
| SS pipes (C=150) | 7 | 16 | 34 | 53 | 101 | 174 | 297 |
| Copper Pipes (C=130) | 6 | 15 | 30 | 51 | 79 | 160 | 265 |
The inner wall of the stainless steel pipe is smooth after the internal and external finishing treatment. The equivalent roughness of the inner wall of the pipe is 0.00152mm, smaller than that of the copper pipes.
Therefore, the use of stainless steel pipe water flow is larger, has more smooth water flow, has better corrosion resistance, and effectively reduces noise.
2. Hygienic Performance
Copper pipe has many advantages, red copper has super antibacterial, and antibacterial performance.
However, if the raw material manufacturing process is not too superb, there may be excessive copper problems, corrosion caused by blue and green water corrosive bitter smell, and scaling phenomenon.
In addition, copper pipes exposed to corrosion for a long time will produce patina, mainly composed of copper carbonate, and copper hydroxide compound [cucO3.Cu (ON)2] and copper sulfate (cusO4), are easy to weather and soluble in water, although they can inhibit fungal action, the effect on bacteria is poor.
Besides, it has convergence, stimulation, and corrosion effect on the mucous membrane in the human body can cause reflex vomiting, and has a strong stimulation effect on the intestinal tract. Modern medical research shows that drinking excessive and high copper water (whether it reaches the degree of blue and green water or not) will do great harm to health.
Stainless steel material is a kind of can be implanted into human body material, safe non-toxic, good clean, put an end to the “red, blue, green water and water hazard water” problem, no odor, its inner surface smooth and not easy to scale, no harmful substances precipitation, after soaking water test, the indicators are in full compliance with relevant standards of drinking water demand, not easy to bacterial infection, more don’t have to worry about water quality is affected, can effectively ensure the health of water quality.
Stainless steel can work safely for a long time below the temperature of -270℃-400℃, no matter be high temperature or low temperature, stainless steel pipes won’t precipitate any harmful material, can be easy to use.
In fact, stainless steel material itself is safe and non-toxic, clean and other characteristics, has long been stainless steel in various fields involving human health for decades of successful application of history fully proved, become a well-known fact.
Decades of practice abroad and laboratory tests in different countries show that the amount of stainless steel metal element precipitation is less than 5% of the standard value stipulated by WHO and European Drinking Water Law (the regulations of all countries in the world refer to these two standards).
Actually, stainless steel pipe is one of the pipes with the best comprehensive performance, a lot of developed countries as early as 70 ’80s had to use stainless steel pipe to undertake water supply, and it reduced leakage rate greatly.
3. Corrosion Resistance
The corrosion resistance of stainless steel pipe is better than copper, can happen with oxidant passivation effect, in the density of surface forming a layer of the tough rich chromium oxide film of chromium trioxide (Cr2O3), to prevent further oxidation reaction occurs, will also be able to maintain good corrosion resistance in the water, even if buried in the ground is still not easy corrosion, service life for one hundred years.
This is the key reason why the corrosion resistance of copper pipe is far less than that of stainless steel pipe.
The copper pipe passivation ability is small and the corrosion resistance is poor, the corrosion is also large when the water flow is large, and there will be harmful substances precipitation.
Copper pipe welding joint can not be the solution, pickling, and passivation on the site, it is difficult to carry out the pipeline internal welding corrosion, so the welding joint is easy to corrosion and aging.
In the use of the copper pipe, the need to control the chemical composition of water and flow rate, water speed should not exceed 2 M/S, otherwise, the corrosion rate will increase significantly, otherwise, it will cause corrosion of the pipe, when the flow rate of 2 M/S, copper pipe corrosion degree is about 3 times of the thin-walled stainless steel pipe, and when the flow rate is greater than 6 M/S,
The corrosion will be 20 times that of a thin-walled stainless steel pipe.
Copper pipe corrosion in PH< 6.5 or residual chlorine content >70ppm of water will greatly increase, in addition, soft water will also lead to increased corrosion.
In addition, the copper pipe surface is also prone to corrosion, as shown in the figure above.
| Content | SS Pipe | Copper Pipe | Note |
|---|---|---|---|
| Passivation in air(O2) | Strong | very weak | SS pipe corrosion resistance principle: the surface has a layer of 10000 of 2-3mmCr2O3 passivation film, once damaged, in the presence of air can immediately form a new oxidation protection film, is the key point of copper tube corrosion resistance. |
| PUVA | Bright appearance, no rust | The exterior produces patina | Stainless steel tube uv resistant, suitable for outdoor riser installation |
| Atmospheric environment corrosion of CO2, H2O, SO2, H2S | non corrosive | corrodible | SS has good adaptability in atmospheric environment, and copper has poor adaptability in atmospheric environment. In general atmospheric environment, copper is easy to corrosion and produce patina |
| Water corrosion - oxygen content in water; Soft water with high acidic PH; Sulfide in hot springs | non corrosive | corrodible | SS has no limit to the chemical composition of water, and has good corrosion resistance to all kinds of oxygen content, temperature and PH value in water. Copper pipe is easy to produce blue water and spot corrosion phenomenon, copper pipe can not be used in warm mineral water |
| Water corrosion - chloride content | ≤200PPm(304) ≤1000PPm(306) | ≤70PPm | The biggest killer of pipe leakage is chloride ion, and the difference between the two is greatly different. The corrosion resistance of copper pipe is less than 1/3 of stainless steel pipe |
| The water corrosion | non corrosive | ≤1.5-2m/s | SS pipe can withstand 30m/s water impact, and copper tube to adapt to the water speed should not exceed 2m/s, 2m/s, copper tube corrosion speed is 3 times of SS pipe, can not be used in soft water all the year round |
| Corrosion of hot water circulation structure | ≥100°C | ≤50°C | Copper pipes corrode more in hot water than in cold water |
4. Economic Value
With the increase in operation time, the oxide layer of copper pipes will be thicker and thicker, and the heat transfer effect will be worse and worse. Stainless steel, on the other hand, does not oxidize at all or oxidizes very slowly. Therefore, if the stainless steel pipe and copper pipe are put into operation at the same time, the longer the operation time, the stainless steel pipe’s economic performance will be better and better than the copper pipe.
Stainless steel pipe prices are generally higher than copper pipe, but once used, almost zero maintenance, in 100 years of life cycle does not need to replace, and other pipe materials can not achieve such a long service life, the overall cost of copper pipe replacement will be stainless steel pipes 2-4 times, this is the stainless steel material in the economy for other materials can not be compared to the greatest advantage, and copper pipe can only be used for 50 years.
Built between 1926 and 1931, the 77-story 318.9-meter Chrysler Building in New York is the world’s first stainless-steel facade.
Despite its coastal and polluted surroundings, the stainless steel still shines after 80 years and has only been cleaned twice in between.
From the Chrysler Building in New York and the Petronas Towers in Kuala Lumpur to the all stainless steel shell of the London Waterloo station in Los Angeles and the London Waterloo station in London, from the 150,000 square meter roof to the 452-meter tall tower, to exquisite decorative pieces and small structural pieces, stainless steel as the most sustainable green building materials, distributed around the world does not have the unique charm of general materials.
These are excellent examples of the timeless properties of stainless steel.
Calculation formula of the theoretical weight of stainless steel:
Weight per meter = (outer diameter – thickness) × thickness × PI × density ÷1000
| Pipe Material | DN | Wall Thickness (mm) | External diameter (mm) | Density g/M³ | Theoretical weight (m) |
|---|---|---|---|---|---|
| Stainless steel | DN20 | 0.8 | 22 | 7.93 | 0.42 |
| Copper | DN20 | 0.8 | 22 | 8.9 | 0.47 |
| Pipe Material | Stainless steel pipe | Copper Pipe |
|---|---|---|
| Serve life/ Year | 70~100 | 30~50 |
5. Application
Application of stainless steel
Stainless steel is not only used for a long time in the food industry, including beverage, dairy, brewing, pharmaceutical industry, tableware, cooking utensils, and other industries, and has become the standard material for these industries, but is also widely used in the material safety and cleanliness requirements of medical human implants such as all kinds of scaffolds, artificial joints and steel nails in the body, etc.
And become the standard material for semiconductor industry cleanroom cleanliness requirements, now more and more hotels also accept the use of stainless steel pipe.
Application of copper
Due to copper reserves in nature being very rich, excellent performance, and having good electrical conductivity, thermal conductivity, copper is used as electrical conductive accessories and heat dissipation accessories of the main material, and become a modern contractor in all residential commercial housing water pipes, heating, refrigeration pipeline installation of the first choice.
Copper is also one of the most easily recycled of all metals, currently accounting for about 40% of the world’s copper supply.
And although stainless steel pipe and copper pipe are pretty good excellent pipe materials, in current use and promotion show, because its comprehensive cost is low, the stainless steel pipe with a high-cost performance ratio can be used in water supply systems not only, also can use as gas pipe, fire control pipes, its application is extensive, far exceed copper pipe.
6. Installation and Environmental Impact
- Copper Pipe: because the copper pipe is welded, the welding joint is easy to rust, so the product is not beautiful in appearance. Moreover, due to the need for embedded installation in the current engineering design, the connection of welding and screw can not meet the requirements of The Times.
- SS Pipe: the pressing type 304L stainless steel pipe can be pressed once, with no residue in the pipe, saving installation time, which is to save cost. Even if argon arc welding is used, there will be no residue inside the pipe.
Summary
In economic efficiency, the stainless steel pipe has more advantages than the copper pipe and has no secondary pollution, long service life, almost zero maintenance, and the impact resistance (tensile strength) of the stainless steel pipe are more than 3 times that of the copper pipes, the corrosion resistance is more than several times of copper pipe, so it is more suitable to use stainless steel pipe as water supply system pipe in building water supply.
