Chloe Zhang
Plastic PEX fittings are a popular choice for plumbing applications, offering a durable and reliable alternative to traditional metal fittings. PEX refers to cross-linked polyethylene, a type of thermoplastic polymer commonly used in tubing and fittings for water conveyance and heating systems. When installing plastic PEX fittings, it's important to consider the specific application and any local regulations. Plastic PEX fittings come in various types, including crimp, push-to-connect, compression, expansion, and press fit. Each type has unique installation methods and tools, such as the use of a power expansion tool or manual hand tools for cold-expansion fittings. Plastic PEX fittings offer advantages in corrosive water conditions and are widely trusted by professionals for their durability, performance, and economic benefits. However, metal fittings remain the preferred choice in certain scenarios, such as UV exposure and proximity to heating devices.
| Characteristics | Values |
|---|---|
| Professional preference | Professional plumbers are increasingly opting for plastic fittings over brass, revealing a growing confidence in the quality and reliability of plastic PEX fittings. |
| Durability | Plastic PEX fittings are widely considered durable, with manufacturers offering comparable warranties to those for brass fittings. |
| Cost | Plastic PEX fittings are much less expensive than brass. |
| Weight | Plastic PEX fittings are much lighter in weight than brass, reducing the need to secure the line as frequently as with brass. |
| Corrosion | Plastic PEX fittings are superior in poor water quality or other corrosive materials in the line, as brass is more prone to corrosion. |
| Heat loss | Brass is particularly prone to heat loss, whereas plastic PEX fittings are better suited for proximity to heating devices. |
| UV exposure | Metal fittings are mandatory in situations with potential UV exposure, as plastic can degrade under prolonged UV exposure. |
| Installation | Plastic PEX fittings are available in Crimp and Cold-Expansion types, each requiring specific tools for installation. |
| Flow restriction | Plastic PEX fittings have a thicker wall requirement, resulting in a reduced inner diameter and restricted flow compared to brass. |
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What You'll Learn
Choosing between plastic and brass PEX fittings
When choosing between plastic and brass PEX fittings, there are several factors to consider. Firstly, cost: plastic fittings are generally cheaper than brass. Secondly, durability: brass fittings are considered more durable and better able to withstand mechanical stress, although they can be susceptible to corrosion depending on water conditions. Plastic fittings, on the other hand, may be weakened by freezing temperatures and can deteriorate when exposed to high levels of UV light, making them less suitable for outdoor use. The type of water in your area should also be considered: brass fittings are better suited for less acidic water, while plastic fittings are recommended for areas with acidic or easily contaminated water to prevent corrosion. It's also worth noting that plastic fittings have a smaller diameter than brass fittings, which can restrict flow. However, this may not be a significant issue depending on your specific application. Finally, ease of installation should be considered, with brass PEX fittings being easier and faster to install.
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Crimp and Cold-Expansion types
Plastic PEX fittings are commonly used in both Crimp and Cold-Expansion types. The main differences between the two are the installation methods and tools used, and the flow passage open area.
Crimp Fittings
Crimp fittings are installed using a copper crimp ring that is placed on the outside of the pipe (PEX-B or PEX-C). A fitting is then inserted inside the pipe, and the ring is crimped using a crimping tool that compresses the copper ring. This method reduces the inner diameter of the passage where the fitting sits, which increases flow restriction and negatively affects flow rate. Stainless pinch clamps can also be used to install crimp fittings, but a different tool is required.
Cold-Expansion Fittings
Cold-expansion PEX fittings are installed by expanding the pipe (PEX-A) and collar using a power expansion tool. Manual hand tools are also available for small jobs. The pipe and collar are expanded, the fitting is inserted, and the pipe and collar are held in position for a short time, allowing them to shrink back down and create a secure and tight seal. This type of fitting does not restrict the flow and has a similar inner diameter as the pipe.
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![[Pack of 25] 1/2 Inch 90 Degree Elbow, Poly PPSU Barb Crimp Pex Fitting, No Lead Plastic Pex Fittings, ASTM F-2159, cUPC Certified. (1/2" Elbow, 25pcs)](https://m.media-amazon.com/images/I/91iGxth2XZL._AC_UY218_.jpg)
Installation methods and tools
Plastic PEX fittings are available in two main varieties: Crimp and Cold-Expansion. The installation method and tools required depend on the type of fitting being used.
Crimp fittings can be installed with a stainless pinch clamp, which requires a different tool than crimp rings. They are cheaper to purchase than brass or stainless steel alternatives, but they have a smaller inner diameter, which increases flow restriction and negatively affects flow rate.
Cold-Expansion fittings are installed by expanding the pipe (PEX-A) and collar, which is placed over the end of the pipe using a power expansion tool. Manual hand tools are also available for small jobs. Once the pipe and collar are expanded, the fitting is inserted and held in place while the pipe and collar shrink back down to create the connection. Cold-expansion fittings are more common than Crimp fittings because they do not restrict flow.
It is important to note that plastic PEX fittings should not be used outdoors or in situations where they will be exposed to high levels of UV light, as the plastic can deteriorate. They should also not be used within 18 inches of water heating devices, as the plastic may not withstand higher temperatures.
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Flow rate and passage
When it comes to installing plastic PEX fittings, understanding the flow rate and passage is crucial. The flow rate refers to the volume of fluid that can pass through the pipe per unit of time, and it is influenced by factors such as pipe size, material, and the number of fittings.
Plastic PEX fittings come in two main types: Crimp and Cold-Expansion. The choice between these types depends on your specific requirements, especially concerning flow rate and the tools available for installation. Crimp fittings utilize different fastening methods and tools compared to Cold-Expansion fittings. One key difference between the two types lies in their flow passage open area. Crimp fittings, made from plastic or metal, have varying standards due to the thicker wall required for plastic. Plastic Crimp fittings have a smaller inside diameter (ID) than their metal counterparts, which can increase flow restriction and negatively impact flow rate. On the other hand, Cold-Expansion fittings are designed to meet the ASTM F1960 standard for both plastic and metal fittings. Plastic Cold-Expansion fittings either match or exceed the minimum inside diameter dimension of metal fittings, ensuring a smoother flow and eliminating flow restriction concerns.
The inside diameter of the fittings plays a significant role in the flow rate. Plastic fittings typically have a smaller ID than brass or stainless fittings, which can impact water flow. However, this can be mitigated by upsizing the fittings to ensure optimal flow rates. Additionally, the number of fittings in line can also affect the flow rate, with more fittings potentially leading to increased flow restriction.
It is important to consider the bending of the PEX pipe, as over-bending can deform its shape, restrict flow, and stress the pipe. The minimum bending radius for a 1/2" PEX pipe with a 5/8" outside diameter (OD) is 5". This consideration is crucial for maintaining the desired flow rate. Furthermore, PEX tubing expands and contracts with temperature changes, so it should be secured with sufficient space to accommodate this expansion, as outlined in the technical specifications.
When deciding between plastic and metal fittings, it is worth noting that plastic fittings are generally cheaper and less susceptible to corrosion from water quality issues. However, metal fittings, such as stainless steel, offer higher strength and reduce the risk of cross-threading or stress cracking. Ultimately, the choice between plastic and metal PEX fittings depends on your specific requirements, taking into account factors such as flow rate, installation methods, and cost.
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Plastic PEX fittings' durability and performance
Plastic PEX fittings are made from high-density polyethylene (HDPE), a type of thermoplastic polymer with a variable crystalline structure. This material is known for its durability and performance, which has led to its widespread use in various applications, including plumbing.
One of the key advantages of plastic PEX fittings is their durability. HDPE is a strong and flexible material that can withstand high temperatures and pressures, making it ideal for plumbing applications. Plastic PEX fittings are also resistant to corrosion, which is a common issue with metal fittings. Brass, for example, is susceptible to corrosion when exposed to poor water quality or other corrosive materials, which can lead to leaks. Plastic PEX fittings eliminate this risk, providing a more reliable and long-lasting solution.
Another benefit of plastic PEX fittings is their performance in maintaining water flow. While plastic fittings have a thicker wall requirement under ASTM2159 Standard, resulting in a reduced inner diameter that can restrict flow, their smooth inner surfaces promote efficient water flow. Additionally, plastic PEX fittings are lightweight, which reduces the need to secure the line as frequently as with metal fittings. This not only simplifies the installation process but also results in cost savings due to reduced material and labour requirements.
However, it is important to note that plastic PEX fittings have limitations. They are not suitable for applications with prolonged UV exposure, as plastic can degrade over time when exposed to UV light. Similarly, plastic PEX fittings should not be used within close proximity to heating devices, as there are concerns about their ability to withstand higher temperatures. In such cases, metal fittings, particularly brass, are still the preferred choice.
Despite these limitations, the trend towards using plastic PEX fittings in plumbing applications is growing. Professional plumbers are increasingly opting for plastic fittings over brass, indicating a broad trust in their durability and performance. The shift is driven not only by economic factors but also by the reliability and longevity that plastic PEX fittings offer, ensuring fewer return visits for repairs.
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Frequently asked questions
PEX refers to cross-linked polyethylene, which is a thermoplastic polymer with a variable crystalline structure. PEX fittings are barbed at one or more end connections and may have male or female pipe threads. They are used to connect PEX tubing to copper tubes, manifolds, faucets, and fixtures.
Plastic PEX fittings offer advantages over brass in certain corrosive water conditions. They are also much less expensive and lighter in weight, reducing the need to secure the line as often. Plastic PEX fittings are also increasingly preferred by professional plumbers, indicating a growing trust in their durability and performance.
The two main types of plastic PEX fittings are Crimp and Cold-Expansion. The main difference between these two types is their installation method and the tools required. Crimp fittings can be installed with a stainless pinch clamp, while Cold-Expansion fittings are installed by expanding the pipe and collar with a power expansion tool, and then inserting the fitting.
