Plastic vs. Brass Fittings for PEX Pipe: Which is Best?

When installing or upgrading a PEX plumbing system, choosing the right fittings is just as important as selecting the pipe itself. The debate over plastic versus brass fittings comes down to factors like durability, cost, water quality, and long-term performance. While both materials have their advantages, using the wrong fitting can lead to leaks, system failures, or costly repairs for certain applications. In this guide, we’ll break down the key differences between plastic and brass PEX fittings, their best applications, and what to consider when making your choice.

What are plastic PEX fittings?

Plastic PEX fittings connect to PEX (cross-linked polyethylene) pipe and are typically made from lightweight and corrosion-resistant materials like polyphenylsulfone (PPSU) or polypropylene. They work well in residential plumbing and hydronic heating systems due to their flexibility and resistance to scale buildup.

Plastic fittings are easy to install using crimp, clamp, or push-fit methods, making them a popular choice for DIYers and professionals alike. However, they may not withstand extreme pressure or temperature fluctuations as well as brass.

Best applications for plastic PEX fittings

One of the features of plastic PEX fittings is their reliable performance in residential applications, including:

• Residential plumbing

• Corrosive water conditions

• DIY installations

What are brass PEX fittings?

Brass PEX fittings are made from a copper-zinc alloy, offering superior strength and durability. They are ideal for high-pressure and high-temperature applications. Brass fittings provide better resistance to mechanical damage and expansion but are prone to corrosion in areas with acidic or high-chlorine water. Though more expensive than plastic, brass fittings are long-lasting and widely used in professional installations.

Best applications for brass PEX fittings

Brass PEX fittings are durable and sturdy, meaning they perform best when used for these applications:

• High-pressure plumbing systems

• Commercial plumbing

• Radiant heating systems

• High-temperature applications

• Outdoor and underground installations

• Well water systems

A closer comparison of plastic and brass fittings for PEX pipe

While brass and plastic PEX fittings have their own unique advantages, making one more suitable than the other for certain applications. Here’s a closer look at these two options.

Durability

Plastic PEX fittings are more resistant to corrosion and scale buildup, making them ideal for areas with high mineral content in water. However, they may be more prone to cracking under extreme pressure or freezing conditions, especially when installed in places with minimal insulation.

Brass fittings are stronger and more durable, especially in high-pressure applications. They can be susceptible to corrosion over time, particularly in areas with acidic or highly chlorine-treated water, but, in general, they have a more impressive lifespan than plastic PEX fittings.

Cost

Plastic fittings are more affordable than brass, making them a budget-friendly yet reliable option for large projects. Brass PEX fittings are more expensive due to material costs, but they provide a long lifespan, which usually justifies the upfront investment.

Performance

Plastic fittings work well in standard domestic projects, from installing a water filtration system to fixing a leak under a sink. Brass PEX fittings provide better overall strength and durability, especially for high-pressure or high-temperature applications. Because they expand and contract less than plastic, you can expect a longer lifespan and lower risk of leaks.

Installation

Brass and plastic PEX fittings often require different installation techniques depending on the connection type. Brass fittings are slightly more difficult to work with due to weight and material hardness, but still relatively easy to install using crimp, clamp, or push-to-connect fittings. Plastic PEX fittings are particularly easy to install and are great for first-time home improvement projects. They’re lightweight and connect PEX pipes easily with push-to-connect fittings.

Temperature resistance

Plastic PEX fittings are designed for standard residential plumbing, but high temperatures (above 200°F/93°C) can weaken them over time. Hydronic heating and hot water systems should use brass PEX fittings rated for high temperatures to prevent premature degradation.

Longevity

Brass fittings last longer in most conditions, especially in outdoor and underground installations. Plastic fittings are durable but more prone to cracking under freezing conditions or excessive force. We also don’t advise burying plastic piping and fittings.

UV exposure and outdoor use

PEX tubing and plastic fittings degrade when exposed to UV light. Direct sunlight or prolonged UV exposure (even indoor lighting with UV emissions) can cause brittleness and cracking. Most plastic fittings are not recommended for outdoor applications unless they are specifically UV-resistant.

Mechanical stress and cracking

Plastic fittings are more prone to cracking under impact compared to brass. Over-tightening during installation or excessive movement in the plumbing system can cause stress fractures in the fittings. Take care when installing these yourself, or consult a professional.

Additional factors to consider when choosing between plastic and brass fittings

Before you hit the hardware store, there are a few other factors to consider when choosing the right fitting for your plumbing project.

Water quality

If your water supply has high chlorine content, plastic fittings are a better choice because they resist corrosion. Brass fittings can corrode over time in such conditions, leading to leaks or failures. To test your water quality, pick up an at-home water testing kit.

Learn more: What Is TDS in Water & Why Should You Measure It?

Lead content in older brass fittings

Brass fittings made before 2014 may contain higher levels of lead, which can contaminate drinking water and pose health risks, particularly for children and pregnant women. If upgrading an existing plumbing system, make sure to replace non-compliant brass fittings with modern lead-free alternatives.

Compatibility

Compatibility can vary depending on the type of PEX and the fitting or connection method used. PEX-A is the most flexible and works well with both expansion and crimp systems, while PEX-B and PEX-C are stiffer and usually paired with crimp or clamp connections. Not all fittings are rated for all PEX types, so it’s important to verify that your chosen fittings and tools match the specific type of PEX you’re using to ensure a secure and long-lasting connection.

Common mistakes homeowners make when choosing between plastic and brass fittings

While these types of plumbing projects can be relatively easy for first-time DIYers, there are a handful of common mistakes we see come up again and again. Here are some of the most common issues we’ve helped with and how you can avoid them in your project.

Mistake #1: Choosing the wrong fitting material for water quality

One common mistake is using brass fittings in areas with highly chlorinated or softened water. These conditions can cause dezincification—a form of corrosion that weakens brass fittings over time, leading to leaks or failures. Plastic fittings are often a safer alternative in such environments.

Mistake #2: Ignoring compatibility with PEX types

Homeowners sometimes assume that all PEX fittings are universally compatible with any PEX pipe type (A, B, or C), but this isn’t always the case. Each type of PEX has specific characteristics and may require different fittings or connection methods. Using mismatched components can compromise performance and longevity.

Mistake #3: Using the wrong connection method

Mixing different connection types—like crimp, clamp, push-to-connect, or expansion—without confirming compatibility can lead to leaks or fitting failure. Each connection method has unique installation requirements and tools, so consistency is key. Incompatible methods can also void warranties or lead to code violations.

Mistake #4: Skipping proper installation techniques

Over-tightening fittings can crack plastic components, while under-tightening may result in slow leaks that go unnoticed for months. Proper torque and technique are essential for a secure, long-lasting connection. Following manufacturer guidelines helps ensure optimal performance and prevents premature failures.

Mistake #5: Not considering temperature and pressure ratings

Plastic PEX fittings aren’t designed to withstand high temperatures or pressures found near water heaters or boilers. Using them in such conditions can lead to deformation or failure. Brass fittings are a better choice in high-stress environments where durability is critical.

Mistake #6: Overlooking UV exposure risks

Plastic fittings and PEX piping degrade when exposed to direct sunlight, even during storage. Prolonged UV exposure makes the plastic brittle, increasing the risk of cracking and leaks. Always store and install PEX components away from sunlight or use UV-resistant materials when necessary.

Mistake #7: Not inspecting or maintaining fittings

Many homeowners believe that once fittings are installed, they’re maintenance-free. However, periodic inspections can catch early signs of wear, corrosion, or leaks before they become serious problems. This is especially important in areas prone to shifting temperatures or water chemistry changes.

Mistake #8: Failing to meet local plumbing codes

Using outdated or uncertified fittings like older brass components with high lead content can lead to violations of local plumbing codes. Non-compliant installations may require costly retrofits or even pose health risks. Always verify that fittings are approved and certified for your region’s building standards.

When to choose plastic PEX fittings

Plastic PEX fittings are ideal for most residential plumbing applications, making up about 90% of the market due to their affordability and ease of use. They’re especially well-suited for water filtration systems, where corrosion resistance is crucial. With innovations like push-to-connect fittings, installation has become quicker and more accessible, significantly changing how homeowners and professionals approach plumbing projects.

When to choose brass PEX fittings

Brass PEX fittings are often the better option when durability and long-term strength are top priorities. They may offer more stability in high-pressure environments, like in rental properties or drinking water systems where reliability is essential. Ultimately, the choice between plastic and brass often comes down to your personal preference and the specific demands of the installation.

Smart plumbing starts with the right fittings

Selecting the right PEX fittings ensures a reliable, leak-free, and efficient plumbing system. By considering factors like water quality, temperature, pressure, and installation environment, you can make an informed decision that ensures long-term durability and performance.

Need some more expert advice? Reach out to Fresh Water Systems with all your plumbing-related questions. With decades of experience in water treatment and filtration, we’ll help you find the perfect solution for your home.

Shop all pipe fittings →

You might also like:

• How to Cut a PEX Pipe

• What is a Quick-Connect Fitting and How Does It Work?

• What is a Quick-Disconnect Fitting and How Does It Work?