Comparing PVC and Stainless Steel Plumbing
When evaluating PVC versus stainless steel pipe and fittings, most consider plastic to be less durable, less resilient, and not as long lived as metal materials, especially stainless steel. However, this is a generalized assumption and can often prove false in many real-world work cases. Comparing a plastic such as PVC to a robust metal like stainless steel may seem foolish to some, but here we will outline the important operation characteristics between the two and demonstrate areas where PVC actually outperforms the metal. When used for approved applications, PVC pipe and fittings can be significantly resistant, durable and provide a service life that can exceed its intended use as well as that of stainless steel.
Below we will outline nine major points comparing PVC and stainless steel plumbing in terms of their individual properties, characteristics, use compatibility, service life and cost.
1) Temperature Tolerance
For temperature based applications, PVC has a reduced maximum and minimum service temperature ratings compared to stainless steel. PVC pipe is approved to handle heat up to 140°F before it begins to soften. The exact temperature range of stainless steel pipe can depend on the metal’s specific grade and composition, but is commonly rated to withstand temperatures of at least 450°F. When heated fluids are expected within the plumbing scenario, stainless steel may make for a better choice over PVC.
When considering low temperature conditions, PVC has a minimum service temperature of 32°F. Temperatures below 32°F lead to lower stress tolerance in PVC pipe and increase the brittleness of PVC making it more susceptible to impact cracking. For PVC pipe, temperatures below 32°F are not recommended due to concerns of fracturing or bursting. Stainless steel being a metal alloy, in contrast does not experience these effects. Stainless steel has a recommended minimum service temperature of -60°F, making it suitable for handling fluids with very low freezing points.
2) Pressure Range
Pipe pressure range ratings are related to the materials’ inherent strength and flexibility, as well as the thickness of the piping sidewall and total diameter. Metals are often more rigid and stronger than plastic materials when dealing with pressure. When high system pressure ranges are expected, stainless steel may make a better choice. PVC can be well suited for pressurized fluid applications if the pressures are within PVC’s reported ranges. Stainless steel pipe can be approved for handling pressures as high as 7815 PSI. While PVC pipe can be rated for internal pressures up to 1230 PSI.
3) Welding and Joining
PVC and stainless steel plumbing have different welding and joining methods that are common to each material. Stainless steel is often mechanically joined through heat fusion soldering or bolted coupling connections. PVC pipework is often chemically joined through use of a primer and solvent cement that welds pipe connections by dissolving and fusing inner and outer surfaces together. Both welding methods have their individual difficulties in execution with the potential for a failed connection, and both when performed accordingly are capable of providing long term, leak proof joints.
4) Mechanical Strength
The mechanical strength and rigidity of stainless steel will outperform that of semi-flexible PVC plastic. The physical toughness of stainless steel is measured to withstand greater stresses over PVC, therefore a greater force will be required to bend and break stainless steel versus PVC pipe.
However, in many applications this is not a concern and sometimes flexibility in the piping run is desired as it can actually make installation easier. In such applications, PVC often makes for a more compatible choice.
5) Chemical Strength and Compatibility
PVC use is not limited to only water supply lines, drains and vents. PVC has a large place in industrial applications and chemical processing, where stainless steel is also largely used. Both materials express noteworthy strength and compatibility for chemicals, which many find surprising for plastics such as PVC. (Consider the following chemical resistance overview for plastics.) For handling chemicals, the viability and/or preference for stainless steel vs PVC will depend on the specific chemical that will flow through the pipe.
The list of potential compatible / incompatible chemicals is too lengthy for a full comparison here. In general, stainless steel is not recommended for strong acids -- hydrochloric acid (HCl) and sulfuric acid (H2SO4) in example. This is due to the potential for flammable, combustible hydrogen gas formation.
PVC on the other hand does not experience this effect and is resistant up to concentrated solutions of HCl and H2SO4. In general, PVC is not recommended for natural oils, hydrocarbons, and food products, where stainless steel reports better compatibility.
Specific chemical suitability of a piping material should always be verified with the manufacturer or supplier prior to use.
6) Corrosion Resistance
By reference definition, plastic materials such as PVC are often described as “non-corrosive” or corrosion resistant compared to metal / steel. This means PVC plastic pipe is not susceptible to environmental corrosion such as the weathering effects of rusting and pitting. While, stainless steel is a corrosion-less material.
As a metal, stainless steel will long term be susceptible to the environmental corrosion that accompanies soil chemistry reactions and elemental chloride exposure that can damage the metal’s integrity through pitting and chemical reactions along its surface.
In contrast, PVC plastic is highly resistant to the effects of soil and chloride reactions, such as those expected when handling seawater and brine solutions; i.e. sodium chloride (NaCl), calcium chloride (CaCl2), magnesium chloride (MgCl2), etc.
7) Insulation Properties and Electrical Conductance
Stainless steel as a metal is an electrical conductor and a relatively poor insulator against thermal changes and ambient temperature influences. This means stainless steel will react to internal and external temperature fluctuations and transfer thermal energy accordingly. A stainless pipe that carries a hot solution will feel warm to the touch, losing heat to the environment, and if ambient temperatures are low, the temperature of the plumbed fluid will also be affected as the metal is cooled.
Alternatively, PVC pipe and fittings are decent insulators against hot and cold thermal exchanges as well as electrical conductance. Fluctuations in external temperatures do not affect PVC as quickly as it affects stainless steel due to PVC having greater thermal insulation properties. Neither will PVC as a material carry an electric current.
8) Service Life
The service life of a piping material is entirely dependent on what the pipe is to be used for as well as environmental stressors of weather exposure and soil chemistry. Pipes used for water will often last longer than pipes used for chemicals but are often exposed to the elements. Pipes protected from external stressors will inherently last longer for service.
Between PVC and stainless steel plumbing, PVC is more resistant to the long term effects of water, weather (excluding sunlight UV exposure), and soil chemistry, which in turn promotes a greater service life for these applications. For non-degradative uses, such as water, PVC can have a life range of 100 years or more. While metals such as stainless steel are long lasting in general, they tend to experience corrosive effects over time that leads to eventual repairs or replacements.
Stainless steel pipe and fittings have a fairly larger purchase price versus PVC based on current cost comparisons. PVC is a lightweight thermoplastic and synthetic material available at low prices, whereas stainless steel is a weighty alloy of metals where the cost will vary on grade and composition.
For 1/2" Schedule 40 piping, PVC can be as low as $0.35 per foot, while comparable size stainless steel pipe prices can be around $6.98 per foot. This is as much as a 20 times greater cost difference. Note, these prices are for small diameter pipe. In general, prices increase with larger size pipes due to more manufacturing material.
Takeaways | PVC vs Stainless Steel Pipes and Fittings
When comparing PVC versus stainless steel pipe and fittings, the plastic can outperform the metal or make a better choice within many common use scenarios. The fundamentals of our comparison, however, indicate each plumbing type has its own strengths and weaknesses that fluctuate based on application. Simply put, stainless steel is better suited for certain work uses while PVC is ideally suited for others.
PVC is considered a non-corrosive material, while stainless steel is a “corrosion-less” material. PVC can be well suited for handling chemicals and has inherent resistance against many acids that stainless steel does not. For water pipe, PVC resists corrosive water interactions, rust and does not as readily support microbiological growth as stainless steel does. In terms of mechanical strength, maximum-minimum operation temperatures, and pressure tolerance, stainless steel has the upper hand. However, PVC excels in terms of insulation to hot cold influences, its resistance to electrical conduction and its ease of installation.
Additionally, plastic materials, such as PVC, are considerably cheaper to purchase, implement and replace. PVC pipe is also much lighter by weight, making it easier to handle, store and install. If looking for top of the line PVC piping and components produced from today’s top manufacturers: we provide it. If you want more information concerning plastic piping, review our resource center. For any further questions, comments or plumbing needs, contact our team of experts today: we are always ready to assist.