Do You Need a Dielectric Union Between Copper and Stainless Steel?

In situations where copper needs to be connected to carbon steel or galvanized steel, flanges or dielectric unions are crucial to ensure electrical insulation between the materials. However, when it comes to the combination of copper and stainless steel, the need for a dielectric union becomes less clear-cut. In most environments, a brass or bronze fitting inserted between the two metals is typically sufficient to provide the required electrical separation. This solution offers a cost-effective and practical way to prevent galvanic corrosion, as well as maintain the integrity and longevity of the connection. Let's dive deeper into the considerations and implications involved in making an informed decision.

Do I Need Dielectric Unions?

If you’re wondering whether you need a dielectric union between copper and stainless steel, the answer is yes. The use of a dielectric fitting isn’t only important to comply with plumbing codes but also to prevent corrosion and leaks. When copper and steel come into direct contact, they can cause a chemical reaction that leads to galvanic corrosion. This corrosion can quickly deteriorate the pipes, causing leaks and other plumbing problems.

Dielectric unions are specifically designed to prevent this galvanic corrosion from occurring. They feature a non-conductive material, such as rubber or plastic, that acts as a barrier between the copper and stainless steel. This barrier prevents the electrical current that causes galvanic corrosion from passing through the pipe connections.

How Does Galvanic Corrosion Occur Between Copper and Stainless Steel?

  • Galvanic corrosion occurs between copper and stainless steel due to their electrochemical differences.
  • When these two metals come into contact in the presence of an electrolyte, such as water or humidity, a galvanic cell is formed.
  • Copper acts as the anode and undergoes oxidation, releasing electrons.
  • Stainless steel, being more noble, acts as the cathode and undergoes reduction, attracting the released electrons.
  • This electron transfer leads to the breakdown of the copper metal, resulting in corrosion.
  • The severity of galvanic corrosion depends on factors like the surface area ratio, the nature of the electrolyte, and the temperature.
  • To prevent galvanic corrosion, it’s essential to use insulating materials or create a barrier between the two metals.

A dielectric union is an essential component used in plumbing systems to separate two dissimilar metal pipes, typically copper and galvanized steel. It’s main purpose is to prevent galvanic corrosion, a corrosive process caused by electrolysis resulting from contact between these dissimilar metals. By interrupting the electrical current, dielectric unions effectively safeguard the pipes, ensuring their longevity and optimal functionality.

What Is a Dielectric Union and Where Is It Used?

A dielectric union is a type of fitting that’s used to separate two dissimilar metal pipes, such as copper and stainless steel. It’s purpose is to prevent galvanic corrosion, which is caused by electrolysis. When two dissimilar metals come into contact with each other, an electrochemical reaction occurs, leading to the breakdown of the metal surfaces and the formation of corrosion.

Galvanic corrosion can be a major issue in plumbing systems, as it can cause leaks and other structural damage to pipes and fittings. By using a dielectric union, the two dissimilar metals are physically separated by a non-conductive material, such as rubber or plastic.

They’re often found in residential and commercial plumbing systems and can be used for both hot and cold water applications.

They’re essential components in situations where dissimilar metals need to be connected, and their use is strongly recommended by industry professionals to ensure the optimal performance and durability of plumbing systems.

How Does Galvanic Corrosion Occur and What Are It’s Effects on Plumbing Systems?

Galvanic corrosion occurs when two dissimilar metals come into contact with each other in the presence of an electrolyte, such as water. The electrolyte acts as a conductor, allowing electrons to flow between the metals. In this process, one metal acts as an anode and corrodes, while the other metal acts as a cathode and remains protected.

In plumbing systems, galvanic corrosion can be a concern when copper and stainless steel come into direct contact. This is because copper is more noble than stainless steel, meaning it’s less likely to corrode. When these metals touch, and water is present, the copper becomes the cathode, and the stainless steel becomes the anode. As a result, the stainless steel corrodes more quickly.

The effects of galvanic corrosion on plumbing systems can be significant. It can lead to leaks, pipe failure, and reduced overall system performance. To mitigate the risk, a dielectric union can be installed between the copper and stainless steel pipes. This union contains a non-conductive material that prevents direct contact between the two metals, reducing the chance of galvanic corrosion.

Source: Dielectric Unions –

Copper and stainless steel are often sought-after for their distinct material properties, making them a popular choice for combining their unique strengths. However, it’s essential to understand how these metals can work together harmoniously and complement each other’s attributes.

Can Copper and Stainless Steel Go Together?

When it comes to joining different metal pipes, one commonly requested combination is copper to stainless steel. Both metals possess unique material qualities that make them remarkably different and exceptionally beneficial when combined. However, due to their dissimilarities, it’s crucial to consider using a dielectric union between copper and stainless steel pipes to prevent potential corrosion and ensure a long-lasting connection.

Copper is known for it’s exceptional thermal conductivity, corrosion resistance, and malleability. It’s commonly used in plumbing applications due to it’s ability to withstand high temperatures and it’s durability over time. On the other hand, stainless steel is revered for it’s strength, resistance to oxidation and corrosion, and aesthetic appeal. It’s often chosen for it’s durability and versatility in various industries, including plumbing.

The compatibility of copper and stainless steel depends on a few factors, primarily the environment in which the pipes will be installed, the presence of electrolytes, and the type of water flowing through the system. If these factors aren’t carefully considered, galvanic corrosion can occur when these two metals are in direct contact, leading to potential leaks, failures, and reduced lifespan of the pipes.

This type of union features a non-conductive material, typically made of plastic or rubber, sandwiched between the copper and stainless steel components. The dielectric union acts as an insulator, preventing direct contact and minimizing the risk of galvanic corrosion.

It’s crucial to carefully follow established industry guidelines, utilize appropriate thread sealants, and ensure proper tightening of connections to maintain the integrity of the system.

By considering the environment, presence of electrolytes, and proper installation techniques, the combination of copper and stainless steel can provide a reliable and durable solution for plumbing systems.


However, it’s important to acknowledge that the specific circumstances and conditions of each situation can vary, so it’s always recommended to consult with professionals or experts in the field to ensure the appropriate measures are taken to prevent potential galvanic corrosion.

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