Does a stainless steel pipe outperform copper?
For years, copper has been the de facto standard for transporting drinking water into buildings.
As science and technology evolve, we often see things in a new light, whether it’s research into health, environmental factors or the evolution of products.
Given this, it’s worth reviewing copper’s use in water transfer solutions and seeing whether there are better options.
In this article, we look at some facts about stainless steel piping and ask the fundamental question:
Is it time to retire copper piping solutions for good?
The case for stainless steel piping over copper
When looking at a piping solution for water and gas transfer, we need pipes that tick all the relevant boxes – strong, sustainable, hygienic, and easy to work with.
As Engineers, we need to be satisfied with the performance properties, but also need to be cognisant that our clients also want a cost-effective solution.
How do the two compare in terms of strength and durability?
Copper is a soft and highly malleable material. This feature can be beneficial in some applications; however, it can pose numerous issues in large water and gas installations. Copper is also more susceptible to damage from external knocks during storage and installation.
Stainless steel is more rigid and 40% stronger compared to copper. Stainless steel doesn’t need as much support as copper because it has greater tensile strength and is 9% less susceptible to thermal expansion on average. It is calculated to reduce bracketing requirements by up to 40%.
Stainless steel can also withstand high-pressure ratings of up to 4000kpa. Copper’s pressure rating reduces dramatically as the size of the pipe increase, making it unsuitable for high-rise buildings.
How do the two compare in terms of cost?
When comparing the cost of raw materials for piping systems, copper and stainless steel have unique advantages and disadvantages. Copper tends to be susceptible to higher cost fluctuations in its raw state, especially in larger sizes.
There is also the issue of welding joints and hot work permits. While some copper pipe joints can be crimped using a press-fit tool, copper sizing is limited to 100mm in press-fit fittings. Conversely, stainless steel press-fit pipes can reach 168mm.
Although press-fit copper can cost approximately 10% less than stainless steel at 15mm, research shows that the cost advantage diminishes as the pipe size increases. For instance, at 28mm, copper costs around 19% more; at 54mm, it costs 22% more; and at 108mm, it costs 24% more. Braised copper typically costs less, but its higher installation cost offsets this.
Theft is a hidden cost as both households and commercial properties can be targeted, where stolen copper is sold for scrap at recycling yards. As long as copper prices continue to rise worldwide, so too will the instances of copper pipe theft.
How do the two compare in terms of sustainability?
Sustainability is another essential factor to consider when selecting materials for piping systems. Stainless steel is a more sustainable option with a low carbon footprint due to its production process without harmful chemicals.
It is also manufactured using a high proportion of recycled material and is 100% recyclable. In contrast, copper is shown to cause problems when recycling, notably as an end-of-life recycling constraint.
How do the two compare in terms of use cases?
Fluids
Another constraint on copper is that it cannot be used in specific applications, such as pipework carrying diesel fuel, where copper can cause diesel to polymerise and thicken.
Pressure
Moreover, the pressure rating of copper pipes reduces dramatically as the size increases.
Velocity
High-velocity systems cannot use copper pipes due to the risk of corrosion, which increases as the flow rate and temperature increases.
Are there positive health impacts of using stainless steel instead of copper piping?
Over the last ten years, research has uncovered that copper ions are released into drinking water where the copper pipe is used.
Studies by the European Commission into which type of pipe had the least emissions leaching into drinking water found that stainless steel fared much better than copper.
While humans can absorb some amounts of copper without adverse health impacts, the older the copper pipes are, the higher the concentration of copper ions released into drinking water through corrosion.
People who come into contact with copper through working with the material or consuming copper ions leached into their drinking water can lead to copper fever, a flu-like condition, and in large quantities, copper poisoning.
Stainless steel does not promote the growth of “biofilm”, which is an essential element for the development of bacteria, whereas copper does.
Another benefit of stainless steel is in the material itself. It has a smooth, hard oxide layer making it hard for bacteria and microorganisms to hide in. Copper’s topography has a surface that promotes bacteria growth as it is easier for the bacteria to find shelter in the material.
Just as copper replaced the use of lead before, likely, stainless steel will eventually replace copper as the material of choice when it comes to function, form and health standpoint.
In many parts of the world, including Switzerland, Germany, Italy and Denmark, the appetite for copper piping is decreasing and being replaced by stainless steel as the material of choice.
Do we need to examine flow rate, and if so, why?
Flow rate is crucial in piping solutions because it determines how much fluid or gas can be transported through the pipeline, it affects pressure and velocity, and impacts the overall performance and reliability of the system.
Proper consideration of pipe diameter, valve size, and pump capacity is necessary to ensure the required flow rate is achieved while maintaining essential pressure and flow conditions.
Stainless steel is corrosion-resistant and is protected by forming a self-repairing passive oxide film. On the other hand, copper is prone to oxidation, leading to corrosion over time.
Additionally, the surface of copper is 17% rougher than that of stainless steel, making it more susceptible to structural corrosion at higher water flow rates.
Water flow above 2 m/s causes structural corrosion in copper. Stainless steel is corrosion resistant, given it takes 6 m/s (which is above the allowable velocity in the Standard) to affect the inner wall of stainless steel, leading to greater efficiency with increased structural integrity.
The graph below shows how water velocity impacts the corrosiveness of the pipe over time. We can see radically different results when comparing copper versus stainless steel piping:
Source: https://blog.waterworksnz.co.nz/stainless-steel-piping-vs-copper-piping
Do we need to examine heat transfer, and if so, why?
Engineers understand that heat transfer is critical in piping solutions as it affects the system’s performance, efficiency, and safety.
Proper heat transfer management is essential to maintain the desired fluid temperature, prevent overheating, and minimise energy losses.
Heat transfer can occur through conduction, convection, or radiation, impacting the piping system’s material selection, insulation, and design. Therefore, understanding and controlling heat transfer is crucial for engineers designing or maintaining piping solutions.
Stainless steel has a lower heat conductivity ratio than copper, making it less susceptible to heat loss. On the other hand, copper requires more insulation to prevent heat loss. Stainless steel’s thermal conductivity is 1/25th that of copper, making it a better choice for applications where heat transfer needs to be minimised.
Source: https://www.researchgate.net/figure/Variation-of-thermal-conductivities-of-copper-and-stainless-steel-with-temperature_fig4_319575524
Case study: Installation of Surepress Stainless Steel press-fit solution for the NSW Maitland Hospital build
The NSW Government commissioned a new hospital build to service the communities of the Hunter Valley NSW and its surrounds, with a project budget close to $500 million.
The Project team and Engineers needed a world-class solution to deliver hot and cold water and gas throughout the hospital’s underlying infrastructure. The brief was to deliver the solution cheaper without compromising on quality and providing a safe work environment at the same time.
Allmach’s Surepress press-fit stainless steel pipe, fittings and custom-fabricated manifolds were chosen to deliver an impressive 15 km of stainless steel pipe.
Being a press-fit installation, safety and expediting of the install were done without the need for hot work permits. Quality assurance procedures were met using the Surepress press-check sleeve film visual confirmation and leak path O-rings. Having a visual quality confirmation made the installation easier and faster, with the comfort of peace of mind the joints were leakproof. The guarantee is an inherent feature of the press-fit solution.
The Surepress system is corrosion-proof, leak-proof and has wash-down properties. The Surepress 316L stainless steel press-fit system made the gas and water pipe installation faster, easier, and safer than traditional copper pipe, saving significant time and money.
The installers could crimp Surepress fittings up to 168mm, an advantage over the copper pipe that can only be crimped up to 100mm – anything larger would need welding.
With extended lengths of service piping throughout supporting the hospital’s infrastructure, the installers avoided extensive bracketing to keep the pipes, as would have been needed with copper piping. The strength and rigidity of our stainless steel pipes were another project that saved installation time and cost, recognised by the construction and installation teams.
Using stainless steel press-fit, the installation saw results 10x faster than conventional welding. This reduced installation time, cutting overall costs by under 30%.
Conclusion
In summary, we have seen the facts and benefits of a press-fit stainless steel piping solution – it outperforms copper in every aspect, from velocity and ease of installation to time and cost savings, all done to the highest quality control standards.
We’ve also seen examples of how some European countries increasingly choose stainless steel over copper for the positive health benefits of stainless steel piping.
Allmach is an Australian piping systems supplier focusing on sustainable infrastructure delivery and innovative solutions, including leak detection.
Allmach is ISO9001 certified and is a major wholesaler and distributor of PVC, Polyethylene, Carbon Steel & Stainless Steel, Aluminium, and pipe, fittings and valves, suitable for the delivery of mains water, wastewater and water treatment, in particular chemical dosing and aeration.
Allmach’s Surepress press-fit piping solution is backed by a 25-year manufacturer’s guarantee, uses AS5200-compliant stainless steel, and is AGA, ActivFire and WaterMark certified.
h2x has collaborated with Allmach so that customers in Australia can design stainless steel piping systems using their product range.
You can learn more about h2x’s design software below.
h2x is design software built to ensure compliance, efficiency, accuracy and collaboration.
The automated calculations for flow rates, velocities, pressures, pump duties, plant sizing, and recirculation systems mean that you can focus on your project’s design instead of undertaking tedious calculations.
h2x’s straightforward user interface helps engineers produce high-quality designs and work more efficiently, all while adhering to industry regulations.
The software has already been used to size millions of kilometres of pipes in projects across the world.
Book a demo with us today to discover how h2x can help you improve your design and calculation workflow.
As New Zealand’s leading supplier of pipeline solutions, customers often ask us “Why should I choose stainless steel pipework over copper?” and, “What are the benefits of stainless-steel vs copper pipework?” In this blog we’ll highlight the strengths and weaknesses of the two piping systems.
When are stainless steel and copper typically used?
Both stainless steel and copper are commonly used and reliable options for pipework. Copper has been used for centuries for domestic, commercial, and light industrial plumbing applications. Stainless steel has historically been viewed as an expensive, premium material and an ‘overkill’ for these applications.
As such, stainless steel piping has traditionally been used more extensively in the food and beverage, and wastewater/water treatment industries, plus heavy industrial applications. Both materials have their advantages, however today; stainless steel is more readily considered for applications where copper piping would have previously been the ‘go-to’ system.
If you’re considering using stainless steel pipe in New Zealand applications instead of copper pipe, here are 13 key qualities and considerations to take into account to help you make an informed decision.
1. Corrosion resistance of stainless steel piping vs copper pipe
Your piping system can suffer from corrosion both internally and externally, and the corrosion resistance of stainless steel pipe is superior to copper pipe for both concerns.
Do copper pipes corrode?
Copper piping systems can corrode externally when exposed to some environmental factors at elevated levels. These include gases such as carbon dioxide, sulphur dioxide, and hydrogen sulphide, along with hard water that’s rich in chlorine, chlorides or a pH outside the 6.5-7 bracket. Acidic environments can cause water discolouration and copper poisoning if it is for human consumption.
Do stainless steel pipes corrode?
Stainless steel piping has very good corrosion resistance. This quality holds in the full range of potable waters, including soft waters. Stainless steel will corrode with high chloride levels but is in general, more corrosion-resistant than copper.
The high level of corrosion resistance in stainless steel comes from a thin, adherent chromium oxide surface film which forms immediately when it comes into contact with oxygen. This sees the pipe surface effectively heal itself if scratched.
In addition to this external surface healing process, piped water supplies contain adequate levels of oxygen to facilitate this healing and protective process inside the stainless steel pipe. The resilience of this chromium oxide layer increases with the presence of molybdenum.
The nickel in stainless steel piping encourages the formation of a crystalline structure called austenite, which aids ductility and formability.
Why does copper turn green?
This is what’s known as oxidation and can occur when copper pipework is exposed to moisture and air. It isn’t harmful, however it is advisable to investigate why the oxidation has occurred as this could point to other problems in the system such as a pinhole leak, faulty join, or dampness in the wall or roof space.
2. Can copper pipe be used for high-velocity applications?
Because the rate of internal corrosion in copper increases significantly as the flow rate increases, copper piping isn’t considered a viable solution for high-velocity applications.
What flow rate is copper pipe suitable for?
At a flow rate of 2 m/s, copper pipe will corrode three times faster than stainless steel pipe. This divide grows exponentially as the flow rate increases, with copper corroding 20 times faster than stainless steel at 6 m/s.
This typically occurs in high-temperature applications where the protective copper oxide layer is softened by the high temperature, then eroded by the water velocity and turbulence. The greater tensile strength of stainless steel gives it a lower susceptibility to internal erosion.
What flow rate is stainless steel pipe suitable for?
Stainless steel piping can withstand water velocities of approximately 30m/s, meaning smaller diameter pipe can be used where suitable.
This is particularly beneficial on variable demand systems where peak demand may only be for very short periods. Here, you can select a pipe size appropriate for standard operation, safe in the knowledge that corrosion resistance will be retained during the higher velocity conditions seen in the short periods of peak demand.
Being able to select a smaller pipe size in these instances can result in attractive capital savings. Selecting a smaller stainless steel pipe size will increase velocity, however, the savings need to be weighed up against any consequent increases in ongoing energy costs required to run the system at a higher velocity.
Acoustic considerations are another potential result of selecting a smaller pipe size and the ramifications should be investigated.
This graph shows the effect of water velocity on the corrosion of stainless steel and copper.
3. Does stainless steel piping require less bracketing?
At scale, the level of bracketing required for piping projects can make a significant difference to material costs and installation timeframes.
Stainless steel doesn’t need as much support as copper because it has a greater tensile strength and is on average 9% less susceptible to thermal expansion. It is calculated to be able to reduce bracketing requirements by up to 40%.
Reducing bracketing is particularly beneficial in commercial plumbing and other building service applications because you have to allow for seismic restraints — a significant cost. Reducing your bracketing requirements can help offset seismic restraint costs and result in big gains in project savings.
Reducing bracketing will likely lead to a saving in labour costs. This is a great way for installers to add value to their design, and is known as value-added engineering. Below is an indication on maximum bracketing distances between Europress stainless steel pipe and copper pipe manufactured to EN 1057 and AS 1432.
Nominal pipe Size (mm)
Europress S/S (m)
Cu EN 1057 (m)
Cu AS 1432 (m)
15
1.5
1.2
1.5
20
2.5
1.8
1.5
25
2.5
1.8
2.0
32
3.5
2.4
2.5
40
3.5
2.4
2.5
50
3.5
2.7
3.0
65
5.0
3.0
3.0
80
5.0
3.0
3.0
100
5.0
3.0
3.0
4. Strength and durability: Is stainless steel pipe stronger than copper pipe?
Stainless steel is on average 2.5 times stronger than copper on strain and stress tests and approximately three times on tensile tests. Our 304L Europress tube has a tensile strength of approximately 650 MPa compared to copper tubing which has a tensile strength of around 280 MPa (Bendable. Annealed is 220 MPa, Hard Drawn is 380 MPa).
Is copper more malleable and easier to cut than stainless steel?
While copper lacks strength, it is more malleable and easier to cut and bend. Annealed 316L pipe can be bent in line with industry best practice, but installers have commented on stainless steel being noticeably harder to cut with a manual cutting tool such as a roller cutter.
There are some ratchet style cutting tools which don’t necessarily cut stainless steel faster but do make it easier and reduce the chance of repetitive strain injury (RSI). Cutter blades tend to wear out quicker when cutting stainless steel versus copper.
What copper gains in malleability, it loses in durability.
Because of the weaker structure of copper it makes the piping more susceptible to damage from external knocks when stored in high foot traffic areas and during installation.
Stainless steel on the other hand, being strong yet ductile, isn't susceptible to the same damage, preserving the integrity of the piping system. Furthermore, stainless steel pipe fittings are stronger making them less susceptible to breakage at what is often the greatest stress point in a piping system.
Because of the strength of stainless steel as a material, you can get away with a thinner pipe wall thickness on your project in order to maintain the same pressure rating when using a smaller external diameter pipe, potentially in the interest of saving on material costs.
Below is a dimensional comparison between copper manufactured to NZS 3501, EN 1057, and AS 1432 and Europress stainless steel showing the outside diameter (OD), internal diameter (ID), and the wall thickness (Wall) with all measurements in mm:
NB
Cu NZS 3501
Cu EN 1057
Cu AS 1432
Europress S/S
O.D.
I.D.
Wall
O.D.
I.D.
Wall
O.D.
I.D.
Wall
O.D.
I.D.
Wall
15
14.73
12.69
1.02
15
13
1
12.7
10.88
0.91
15
13
1
20
21.08
19.04
1.02
22
20
1
19.05
17.01
1.02
22
19.6
1.2
25
27.43
25.39
1.02
28
25
1.5
25.4
22.96
1.22
28
25.6
1.2
32
34.19
31.75
1.22
35
32
1.5
31.75
29.31
1.22
35
32
1.5
40
40.54
38.1
1.22
42
39
1.5
38.1
35.66
1.22
42
39
1.5
50
53.24
50.8
1.22
54
50
2
50.8
48.36
1.22
54
51
1.5
65
65.94
63.5
1.22
66.7
62.7
2
63.5
61.06
1.22
76
72
2
80
79.45
76.61
1.42
76.1
72.1
2
76.2
72.94
1.63
88.9
84.9
2
100
105.7
102.4
1.63
108
103
2.5
101.6
98.34
1.63
108
104
2
125
N/A
N/A
N/A
N/A
N/A
N/A
127
123.7
1.63
139.7
135.7
2
150
156.1
152.4
1.83
N/A
N/A
N/A
152.4
148.3
2.03
168.3
164.3
2
5. Does stainless steel cost more than copper?
The cost of stainless steel as a raw material is more stable than copper. It’s becoming increasingly common for stainless steel pricing to be competitive with copper, especially on the larger sizes, because copper tends to be susceptible to higher cost fluctuations in its raw state.
We have found in the past that the price of Europress stainless steel pipe system was slightly more than copper pipe up to 28mm (the equivalent of 1”/25mm). Then, above 28mm, Europress became more cost-effective than press-fit copper, and increasingly so as the sizes increased.
Research has shown that press-fit copper costs approximately 10% less than stainless steel at 15mm, 19% more at 28mm, 22% more at 54mm, and 24% more at 108mm. Braised copper will typically have a lower cost, however this is offset by its higher installation cost.
6. Is copper pipe suitable for chlorinated water supplies?
Christchurch has been experiencing issues with copper hot water cylinders failing in the thousands since the council began chlorinating the city’s water supply in March 2018. A University of Canterbury study found chlorine (along with other factors) contributed to pitting corrosion inside the copper cylinders.
Plumbers in the garden city who have been replacing the failed copper water cylinders are replacing them with steel units, which are said to be more reliable.
Deeper investigation across the country found a difference in locations where the town or city water supply was from a bore water source or from a surface water source such as a lake or river. Locations which had a surface water supply didn’t have issues with copper, like areas which had a bore water supply. This was particularly an issue when dealing with hot water.
7. Stainless steel pipe vs Copper pipe: which is more sustainable?
Stainless steel is a sustainable material which can be recycled and reused. It has a low carbon footprint because it can be produced without using harmful chemicals. It is also manufactured using a high proportion of recycled material and is 100% recyclable.
Copper is a sustainable material with a low carbon footprint too, but it can cause environmental pollution if not disposed of correctly, e.g., when buried some soils will break copper down, leaching it into the soil.
8. Are there applications where copper can’t be used?
Copper can’t be used in the following applications:
- Pipework carrying diesel fuel – the copper can cause diesel to polymerise and thicken.
- High-pressure systems – the pressure rating of copper pipe reduces dramatically as the size increases.
- High-velocity systems can’t use copper pipe due to the risk of corrosion, which increases as flow rate increases.
9. Does stainless steel offer improved heat retention?
Thermal conductivity is how fast heat will travel outward through the diameter of a piping material. For example, if you are running a copper hot water line into a factory you may need to have a higher input temperature to ensure you get the correct output temperature because the heat loss through a copper line will be higher.
Heat will transfer (and be lost) a lot faster through copper piping, which means insulation is a lot more important to prevent heat loss and related increases in heating costs. Stainless steel thermal conductivity is 1/25th that of copper.
This means stainless steel requires less insulation measures, reducing insulation material and installation costs.
10. Stainless steel needs chloride-free insulation
It’s been proven that stainless steel is susceptible to deterioration from high concentrations of chlorides, particularly in applications over 60°C. This makes selecting the correct insulation very important as some brands of insulation contain chlorides.
When selecting an insulation for stainless steel pipework, it’s recommended that you choose one which is free from chloride. Like stainless steel, copper is also susceptible to deterioration from high concentrations of chlorides in insulation.
11. Bore Smoothness: is stainless steel superior to copper?
Stainless steel piping has a smoother bore or lower roughness factor, making it less susceptible to the growth of bacteria than copper piping.
Not only does copper have higher frictional loss from this roughness factor, it is also more susceptible to bacteria growth which means higher levels of water treatment are required.
12. Connecting copper with plastic piping systems
Deterioration or even failure has occurred in plastic piping systems when connected to a copper system resulting from copper leaching — especially on high temperature and high-velocity applications. This can cause extensive damage to the plastic piping, in some situations creating terminal pin-holing damage in the plastic.
Given stainless steel is less susceptible to erosion from high velocity and high temperatures, there is no risk of leaching and subsequent damage to connecting plastic pipework.
13. Can you connect stainless steel pipe with copper pipe?
There’s a wide school of opinions on this topic. Copper is a non-ferrous material, so, if designed correctly it is ok to connect stainless steel and copper piping.
However, if the system is running at high temperatures or high velocity, or if the water quality is poor; copper leaching can occur. This needs to be considered on a project-by-project basis.
If you decide stainless steel is the right fit for your next project, browse our range of Europress stainless steel piping system products. The comprehensive range features stainless steel tube, stainless steel pipe fittings, brackets, valves, seals, flanges and stainless steel pipe tools.