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Failing Hydronic Heat Piping: Causes and Solutions

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COMMON PIPE PROBLEMS

Understanding Failing Hydronic Heat Piping and the Advantages of Oxygen Barrier PEX Systems

Hydronic heating systems are a popular and efficient way to heat homes and buildings, but they can experience failures due to various factors including the type of piping used. Some common types of piping that may fail in hydronic heating systems include polybutylene, Kitec, Aquatherm, Entran II, and copper. In this article, we will explore the reasons behind these failures and discuss why using a pipe with an oxygen barrier, such as Uponor’s hePEX system, is an optimal solution for replacing failing systems.

Failed polybutylene hydronic radiant heating system versus new PEX hydronic radiant heating system replacement

Common Causes of Hydronic Heating System Failures

Hydronic heating systems can fail for several reasons, including:

· Corrosion: Over time, the pipes in a hydronic heating system can corrode leading to leaks and reduced efficiency. Corrosion can be caused by a variety of factors, such as high water pH levels, the presence of dissolved oxygen in the water, and the use of dissimilar metals in the system.

· Galvanic Corrosion: (See Table Below) Galvanic corrosion is a specific type of corrosion that occurs when two dissimilar metals are in contact with each other in the presence of an electrolyte, such as water. In hydronic heating systems, this can happen when copper pipes are connected to steel components, such as radiators or boilers. The difference in the electrical potential between the two metals causes an electron flow from one metal to the other, resulting in corrosion of the less noble metal (usually the steel component). This type of corrosion can lead to leaks, reduced efficiency, and premature failure of the system components. To prevent galvanic corrosion, it is important to use dielectric unions or fittings when connecting dissimilar metals or to use the same metal throughout the system.

· Thermal Stress: Hydronic heating systems are subject to frequent temperature changes, which can cause the pipes to expand and contract. This thermal stress can lead to cracks and leaks in the piping, especially if the pipes are not properly supported or if they are made of materials that are not suitable for use in hydronic heating systems.

· Poor Installation: Improper installation of hydronic heating systems can lead to a variety of problems including leaks, reduced efficiency, and premature failure of the pipes. This can occur if the pipes are not properly sized, if they are not adequately supported, or if they are not installed according to the manufacturer’s specifications.

Galvanic Corrosion Table

Galvanic corrosion chart showing noble and less noble metals in hydronic heating systems

When two dissimilar metals are in contact with each other in the presence of an electrolyte (such as water), galvanic corrosion can occur. The metal higher on the galvanic series (more noble) will act as the cathode, while the metal lower on the series (less noble) will act as the anode and corrode preferentially.

In the galvanic corrosion chart, the metals are arranged vertically according to their nobility. The further apart two metals are on the chart, the greater the difference in their nobility and consequently, the higher the risk of galvanic corrosion when these metals are coupled together. For example, if magnesium (at the bottom of the chart) is in contact with platinum (at the top of the chart), there will be a significant risk of corrosion for the magnesium as it is much less noble than platinum.

To minimize the risk of galvanic corrosion, it is best to choose metals that are close together on the galvanic series when designing systems where dissimilar metals may come into contact with each other.

Failing Piping Systems in Hydronic Heating

Several types of piping commonly used in hydronic heating systems have been known to fail prematurely, leading to costly repairs and replacements. Some of these include:

Polybutylene (PB) pipes were widely used in hydronic heating systems from the 1970s to the 1990s. However, these pipes were found to be prone to premature failure due to their sensitivity to chlorine and other additives commonly found in municipal water. When exposed to these chemicals, polybutylene pipes ‘dry out’ and develop cracks, causing leaks and ultimately system failures.

In the 1990s, the class action lawsuit Cox v. Shell was filed against Shell Oil Company, the manufacture of polybutylene pipes. The lawsuit alleged that Shell had knowingly supplied defective materials and failed to warn consumers about the potential risks associated with polybutylene piping systems. Shell agreed to pay for the replacement of polybutylene plumbing systems in homes and buildings across the United States.

Polybutylene pipe with visible manufacturer's code printed on the side, used for identifying the presence of polybutylene plumbing in homes and buildings.

It is important to note that polybutylene pipes were never intended by the manufacturer to be used in hydronic heating systems. The high water temperatures and pressures in these systems accelerate the degradation of polybutylene pipes, leading to even more rapid failure. Consequently, the replacement of polybutylene pipes in hydronic heating systems was not covered by the Cox v. Shell class action lawsuit settlement.

Kitec piping, which consists of a layer of aluminum sandwiched between two layers of plastic, was used in hydronic heating systems from the 1990s to the early 2000s. The fittings used in Kitec piping systems were made of brass components, which contained a high percentage of zinc and were particularly susceptible to a type of corrosion called dezincification. Dezincification occurs when the zinc in the brass alloy is selectively leached out by the water in the hydronic heating system, leaving behind a porous and weakened copper structure. This process is accelerated by high water temperatures, chlorine content, and other factors associated with hydronic heating systems. As the brass fittings degrade, they become more prone to leaks and failures, compromising the integrity of the entire piping system.

Kitec pipes in orange and blue with visible markings for identification

In addition, the aluminum layer in Kitec piping can react with the water in the system, leading to the formation of aluminum oxide and further corrosion. This reaction is caused by the inherent instability of aluminum in the presence of water and other chemicals, which can cause the metal to oxidize and deteriorate over time. As the aluminum layer corrodes, it can cause the plastic layers of the piping to delaminate and fail resulting in leaks and system failures.

Entran II

Entran II: Entran II is a type of flexible polyethylene piping that was used in hydronic heating systems during the 1980s and early 1990s. This piping system was designed to be a cost-effective alternative to traditional copper piping. However, Entran II piping was found to be prone to premature failure due to its sensitivity to oxidation and its tendency to become brittle over time. The high water temperatures in hydronic heating systems, which typically range from 140°F to 180°F (60°C to 82°C). At these elevated temperatures, the oxidation rate of the polyethylene material is accelerated, causing the piping to degrade more rapidly.

Cracked Entran II pipe due to brittleness in hydronic heating systems
Entran II piping identification markings and labels for hydronic heating systems

As the piping degrades, it loses its flexibility and becomes more susceptible to cracking and leaking under the stress of the hot water flowing through the system. The repeated thermal expansion and contraction of the piping during heating cycles further exacerbate the problem, leading to an increased risk of system failures and potential water damage to the surrounding areas. Many homeowners and building owners have had to replace their Entran II piping systems due to these issues, often at significant expense. To mitigate the risks associated with Entran II piping in hydronic heating systems, it is recommended to replace the piping with a more suitable material such as cross-linked polyethylene (PEX) which can better withstand the high water temperatures and thermal stresses encountered in these applications.

Copper: Copper piping is prone to corrosion under certain conditions, like when it is exposed to high levels of dissolved oxygen in the water or when the water has a high pH level. Corrosion can lead to pinhole leaks and eventual system failure.

In some cases, Type M Copper was used during installations of hydronic heating systems. Type M copper has thinner walls compared to Type L or Type K. The thinner walls of Type M copper make it more susceptible pinhole leaks, as Type M Copper is not suitable for pressurized systems

Corroded copper piping with thin walls due to pitting in hydronic heating systems

To minimize the risk of failures and ensure the longevity of your hydronic heating system, it is recommended to consider replacing your copper piping with cross-linked polyethylene (PEX) piping. PEX piping is a durable, flexible, and corrosion-resistant alternative to copper that is well-suited for use in hydronic heating systems. PEX is easier to install than copper, as it requires no soldering and can be connected using simple crimp or expansion fittings. PEX is less susceptible to damage from thermal expansion and contraction, which can help to reduce the risk of leaks and failures over time. By replacing your copper hydronic heating system with PEX piping, you can improve the reliability and efficiency of your system while also reducing the likelihood of costly repairs and replacements in the future.

Aquatherm: Aquatherm is a type of polypropylene piping that has been used in hydronic heating systems. Aquatherm systems have experienced failures when used in conjunction with copper components. When copper piping or components are used in the same system as Aquatherm polypropylene piping, the copper can cause the Aquatherm piping to fail prematurely. This is due to a process called “chloride stress corrosion cracking” (CSCC), which occurs when copper ions, released from the copper components, react with the chlorine in the water and attack the polypropylene piping. This chemical reaction causes micro-cracks to form in the Aquatherm piping, leading to leaks and system failures.

Aquatherm 3 Inch 90 Degree Fitting - Image depicting aquatherm piping and fittings for educational purposes.

In many hydronic heating systems, heat register components such as finned tubes or baseboard heaters are made of copper. When these copper components are used in conjunction with Aquatherm polypropylene piping, the rate of CSCC can be accelerated leading to even faster deterioration of the Aquatherm piping. The higher temperatures in these areas of the system can also contribute to the increased rate of failure.

To prevent this issue, it is crucial to ensure that Aquatherm polypropylene piping is not used in the same system as copper components including heat registers. If copper must be used in a hydronic heating system, it is recommended to use a different type of piping material that is compatible with copper such as cross-linked polyethylene (PEX) or stainless steel.

The Benefits of Oxygen Barrier PEX Piping

To address the issues associated with failing hydronic heating systems, many professionals recommend replacing the existing piping with a system that incorporates an oxygen barrier such as Uponor’s hePEX piping. Oxygen barrier PEX piping offers several advantages over traditional piping materials:

· Corrosion Resistance: PEX piping is highly resistant to corrosion, as it does not react with the water or the chemicals commonly found in hydronic heating systems. This means that PEX piping is less likely to develop leaks or suffer from premature failure due to corrosion. Additionally, PEX piping is not susceptible to galvanic corrosion, as it is a non-conductive material and does not promote electron flow between dissimilar metals.

· Flexibility: PEX piping is flexible, which allows it to be easily routed through tight spaces and around obstacles. This flexibility also helps to reduce the risk of damage due to thermal stress, as the piping can expand and contract without developing cracks or leaks.

· Oxygen Barrier: Uponor’s hePEX piping features an oxygen barrier that prevents dissolved oxygen from entering the water in the system. This is important because dissolved oxygen can promote corrosion in other components of the hydronic heating system, such as the boiler or radiators. By preventing oxygen from entering the system, hePEX piping helps to extend the life of the entire system.

· Easy Installation: PEX piping is easy to install, as it can be cut to length on-site and connected using simple crimp or compression fittings. This can help to reduce the risk of installation errors and ensure that the system is installed according to the manufacturer’s specifications.

· Cost-Effective: While replacing a failing hydronic heating system can be a significant investment, using oxygen barrier PEX piping can help to reduce the overall cost of the project. PEX piping is generally less expensive than copper or other traditional piping materials and its ease of installation can help to reduce labor costs.

Choosing the Right Replacement Piping System

When replacing a failing hydronic heating system, it is important to choose a piping system that is designed to withstand the unique challenges of hydronic heating. Oxygen barrier PEX piping, such as Uponor’s hePEX system, is an excellent choice for several reasons:

· Proven Performance: Uponor’s hePEX piping has been used in hydronic heating systems for over 20 years and has a proven track record of reliability and durability.

· Comprehensive System: Uponor offers a complete system of hePEX piping, fittings, and accessories, which ensures compatibility and optimal performance.

· Warranty: Uponor offers a comprehensive warranty on its hePEX piping, which provides peace of mind and protection against defects or failures.

When selecting a replacement piping system for a hydronic heating system, it is important to work with a qualified professional who has experience with these types of systems. They can help to assess the specific needs of the system and recommend the best piping material and configuration to ensure optimal performance and longevity.

Addressing Failing Hydronic Heat Piping

Failing hydronic heating systems can be a significant source of stress and expense for homeowners and building managers. By understanding the common causes of these failures including corrosion, galvanic corrosion, thermal stress, poor installation, the use of problematic piping materials like Entran II, and the advantages of oxygen barrier PEX piping, it is possible to make informed decisions about repairing or replacing these systems. Uponor’s hePEX piping is an excellent choice for those looking to replace failing systems as it offers superior corrosion resistance, flexibility, and ease of installation. By investing in a high-quality replacement piping system, it is possible to ensure the long-term reliability and efficiency of a hydronic heating system.

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