Why is PEX plumbing bad? Hidden risks you should know about

PEX is commonly used in modern home plumbing: it’s flexible, affordable, and easier to install than traditional materials like copper or PVC.

Still, its growing popularity hasn’t stopped some homeowners from asking, “Why is PEX plumbing bad?”

Keep reading to learn about the hidden risks you should be aware of, and whether it’s worth the trade-off compared to traditional materials.

What is PEX plumbing, and why is it popular?

PEX plumbing stands for cross-linked polyethylene plumbing. At its core, PEX is a high-density polyethylene whose polymer chains are chemically bonded together, creating a type of plastic tubing commonly used in modern homes. This cross-linking process enhances the material, making it a viable alternative to traditional materials, such as copper, polyvinyl chloride (PVC), and chlorinated polyvinyl chloride (CPVC).

One of the primary reasons PEX has become so popular in modern construction is its flexibility. Unlike copper or PVC, which require multiple fittings and connectors to go around corners or obstacles, PEX tubing and PEX hose can bend and curve easily without breaking. This makes installation faster, less invasive, and reduces the number of joints where leaks could eventually occur. 

PEX is also more affordable than traditional piping materials, and labor costs are reduced since contractors can install PEX with fewer tools and in less time.

Another key benefit is PEX’s resistance to scale buildup, rust, and corrosion. These issues plague copper and galvanized steel plumbing over time, especially in areas with hard or acidic water. However, the inner surface of PEX is smooth and non-reactive, allowing water to flow through it more efficiently with a reduced risk of clogs or pipe damage.

Despite these advantages, some homeowners and professionals have raised concerns about its safety, longevity, and environmental impact.

Common concerns with PEX plumbing

Like any material, plumbing with PEX comes with limitations that are important to understand, especially if you're planning a significant project or considering it for your home’s entire water supply system. Let’s take a closer look at these concerns.

Chemical leaching and water quality

PEX is a plastic-based material, so there is a risk that substances used in its manufacturing, such as volatile organic compounds (VOCs), could seep into the water supply over time. A specific example is styrene, a VOC that has been found to leach from certain types of PEX tubing, particularly when the pipe is new or exposed to high water temperatures. These compounds can affect the smell and taste of drinking water, and in rare cases, raise health concerns, especially for individuals with sensitive immune systems or those who use untreated tap water.

In addition to VOCs, PEX can also release substances that increase total organic carbon (TOC) levels in water. Higher TOC levels in portable water indicate the presence of unwanted organic material, which serves as food for bacteria.

UV sensitivity and limited outdoor use

PEX is highly sensitive to ultraviolet (UV) light, which means it’s not designed for outdoor or above-ground use where sunlight is present. Even indirect exposure to UV rays through a window or a partially open wall can cause the material to degrade over time, making it brittle and prone to cracking or failure. For this reason, PEX should always be stored away from sunlight before installation and used only in walls or underground.

Rodent damage and durability issues

Rodents, such as rats and mice, are known to chew through various materials, and unfortunately, PEX tubing is no exception. Unlike copper, which is tough and deters gnawing, PEX is a softer plastic that rodents can bite through with little effort. If they find their way into your attic, basement, or crawl space, they might treat your water lines like a chew toy, leading to slow leaks or sudden pipe bursts.

Additionally, durability is another concern some homeowners have with PEX. Since it’s a plastic material, it can be affected by chemical and environmental factors, such as high heat, freezing temperatures, UV exposure, or high water pressure. For instance, when exposed to high levels of chlorine in treated municipal water over long periods, some types of PEX tubing may degrade or become brittle. 

PEX installation drawbacks

Installing PEX requires careful planning, the right tools, and attention to detail. If not done properly, its most significant strengths—flexibility and simplicity—can quickly turn into weaknesses.

Issues with fittings and joints

Connecting PEX tubing securely requires crimped or clamped fittings, which can be a source of trouble if not installed properly. Over-tightening a clamp, using the wrong type of fitting, or failing to align the pipe can weaken the joint and cause it to fail over time. Since many PEX lines are hidden behind walls or under floors, leaks at the joints can often go undetected until significant damage has occurred.

PEX also has a maximum bend radius, meaning you can’t bend too sharply without stressing the pipe. If the tubing is forced into tight corners or bent beyond its limits, it can weaken the structure and create pressure points that fail later. Additionally, PEX expands and contracts differently than the plastic or brass fittings used with it. Over time, temperature fluctuations can cause the seal between the tubing and fitting to loosen, resulting in drips or full-scale leaks.

Temperature and pressure limitations

PEX is not ideal for high-heat or high-pressure environments. It begins to deteriorate after prolonged exposure to water temperatures above 180°F, which can be common in systems with tankless water heaters or radiant floor heating. At high temperatures, the pipe’s pressure rating also drops, increasing the risk of bursting or premature failure.

To avoid this, plumbers often install metal connectors between PEX lines and water heaters to prevent leaks. These connectors act as a heat buffer, keeping the tubing from being exposed directly to extreme temperatures. 

Difference between PEX A and PEX B

There are several types of PEX on the market, but the two most common are PEX A and PEX B. While they may look similar at a glance, they differ in how they’re made and how they perform in a plumbing system. 

The main difference lies in the manufacturing process. PEX A is made using the Engel method, also known as the peroxide method, which chemically cross-links the polyethylene molecules during the extrusion process. This results in a higher degree of cross-linking, making the tubing more flexible and resilient. 

On the other hand, PEX B is formed using the silane method, also known as the moisture-cure process. In this method, cross-linking occurs after extrusion, and the cross-linking percentage is typically lower, resulting in a stiffer structure for PEX B.

In practical terms, PEX A is more flexible, making it easier to install in tight spaces or around corners without needing many fittings. It’s also more resistant to bursting in cold climates than PEX B.

However, PEX B is more rigid and holds its shape better, which can make installation easier in straight runs. It’s also more widely available and often chosen for large-scale plumbing projects due to its lower price. 

Overall, both types of PEX are safe for potable water and meet plumbing codes in most areas, but neither is entirely immune to degradation under exposure to high chlorine levels or UV light, chemical interactions, or rodent damage.

PEX vs copper: is it really worth the trade-off?

PEX may be the modern favorite, but copper still has a loyal following, and for good reason. Copper is known to last 70 to 80 years when properly maintained. One of its standout qualities is its natural resistance to bacteria, which makes it a better choice for drinking water. It’s also fully recyclable, so even if it’s removed during a remodel or home upgrade, the material can be repurposed or sold rather than ending up in a landfill.

On the other hand, PEX is easier to install, requires fewer fittings, and is cheaper upfront. This makes PEX appealing for DIYers or contractors looking to work quickly and cost-effectively. However, it may incur higher costs over time if repairs are required, as it's more vulnerable to rodent damage, chemical degradation, and leaks at fittings if installed improperly.

Insurance and resale value also tip the scale. Some insurers favor copper for its fire resistance and durability, which may influence premiums. Additionally, in specific markets, buyers view copper as a sign of higher-quality construction. Hence, while PEX is gaining wider acceptance, it may not carry the same level of trust or resale appeal in older or high-end homes.

Final verdict: Is PEX plumbing a smart choice?

PEX can work well if properly installed, but it comes with trade-offs. Its flexibility, low cost, and ease of installation make it a practical choice for many homeowners who prioritize affordability and speed. However, it may not offer the same level of long-term durability, resale appeal, or resistance to damage as traditional materials like copper. Whichever you choose, understand the pros and cons first, as outlined in this article, and work with a professional plumber.