Connecting copper fittings to galvanized steel pipe is possible, but it requires some special considerations. Galvanized steel pipe has a zinc coating that protects it from corrosion. However, joining it to copper can lead to galvanic corrosion over time. With proper joint preparation and the use of dielectric unions or other insulating fittings, copper and galvanized steel pipe can be used together safely in plumbing systems.
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Quick Answers
– Yes, copper fittings can be used with galvanized steel pipe, but dielectric unions or other insulating fittings should be used to connect them.
– Galvanic corrosion can occur between copper and galvanized steel due to their different metals. This can lead to leaks over time.
– Dielectric unions, plastic fittings, or short jumper wires can break the metal-to-metal contact and prevent galvanic corrosion.
– Proper joint cleaning, use of compatible thread sealants, and following manufacturer instructions are also important when joining copper to galvanized steel pipe.
Galvanic Corrosion Concerns
The key concern when joining copper and galvanized steel plumbing is galvanic corrosion. Galvanic corrosion happens when two dissimilar metals are in contact in the presence of an electrolyte – in plumbing, this electrolyte is water.
Galvanized steel pipe is coated with a thin layer of zinc to protect the underlying steel. The zinc is more “anodic” than copper in the galvanic series. This means zinc will corrode preferentially when connected to copper.
Over time, the zinc coating will get eaten away, exposing the steel underneath to corrosion. This can lead to leaks and loss of structural integrity of the galvanized piping.
To prevent galvanic corrosion, metal-to-metal contact between the copper and galvanized steel must be avoided. This is most commonly done using dielectric fittings.
Dielectric Fittings
Dielectric fittings contain an insulating material that breaks the electrical connection between the two dissimilar metals. Common types of dielectric fittings include:
– Dielectric unions – Have a plastic liner that separates the end connections. Allow easy disconnect for maintenance.
– Dielectric coupling – A short plastic sleeve that insulates the joint. Does not allow disconnect.
– Plastic fittings – Teflon or PVC fittings replace galvanized steel connectors. Avoid metal-to-metal contact.
– Dielectric nipples – Short section of plastic pipe to replace a galvanized nipple between copper joints.
By using an appropriate dielectric fitting at each copper-to-galvanized transition, galvanic corrosion can be prevented. The metal pipe ends never make direct contact.
Jumper Wires
Another option is to connect copper and galvanized steel plumbing using short jumper wires. The wires allow the metals to connect electrically but avoid metal-to-metal contact.
The wires are attached to each pipe near the connection point. This equalizes the electric potential between the copper and galvanized sections and provides a path for any galvanic currents to flow without corroding the metals. Jumper wires are less convenient than dielectric fittings but can also effectively break the metal-to-metal joint.
Proper Connection Methods
To create a sound joint between copper and galvanized steel:
– Thoroughly clean pipe ends with emery cloth to expose bare, shiny metal. Remove any dirt, grease, or corrosion.
– Apply pipe thread sealant tape or paste compatible with both metals. Avoid contaminating fittings.
– When tightening joints, use two wrenches to avoid putting stress on the piping. Tighten to manufacturer torque specifications.
– Use Teflon tape on pipe threads to provide a leak-free seal. Ensure tape does not get into the fitting.
– Follow manufacturer instructions for any insulating fittings like dielectric unions. Make sure they are installed correctly.
– Attach any jumper wires securely to cleaned pipe sections near the joint.
Proper assembly helps prevent leaks and ensures maximum electrical insulation between the pipe metals.
Location of Joints
Where copper-to-galvanized joints are located also impacts the risk of galvanic corrosion:
– Joints under sinks or other wet areas have more leakage current risk. Dielectric couplings or unions are preferred here over plain jumper wires.
– Underground joints have greater corrosion risk due to soil moisture. Plastic piping or fittings are ideal for buried galvanized-to-copper transitions.
– Connections in drain lines have less water contact. Jumper wires or dielectric nipples can suffice in these dryer locations.
For critical applications, consider using an entire non-metallic piping section between copper and galvanized. Plastic adapters allow transitions at each end without any direct metal contact in between.
Inspection and Maintenance
Periodic inspection of copper-to-galvanized joints can detect potential leaks before they become severe. Signs of corrosion include:
– White/blue-green buildup at joints as zinc corrosion accelerates.
– Rust staining or drips near joints as steel corrosion begins.
– Weeping or dripping joints as corrosion creates leaks.
Catching corrosion early allows for joint refurbishment. This may involve:
– Disconnecting and cleaning corroded joints.
– Replacing worn dielectric fittings.
– Adding joint insulation if none existed before.
– Checking jumper wire connections are intact.
– Checking for adequate grounding elsewhere in the plumbing system.
With proper initial installation and ongoing monitoring, copper and galvanized pipe can coexist successfully. But care must be taken to avoid galvanic corrosion through insulating techniques.
Conclusion
Joining copper and galvanized steel pipe is possible by using dielectric fittings or jumper wires. These break the metal-to-metal contact to avoid galvanic corrosion between the dissimilar metals. Proper assembly, strategic location of joints, and periodic inspection also help minimize corrosion risk. With the right approach, copper fittings can be safely used on galvanized pipe plumbing systems.
| Method | Pros | Cons |
|---|---|---|
| Dielectric Unions |
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| Dielectric Couplings |
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| Plastic Fittings |
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| Jumper Wires |
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Key Points
– Use dielectric fittings like unions or couplings when joining copper to galvanized steel pipe.
– Alternatively, short jumper wires can connect the metals electrically while keeping them isolated.
– Ensure joint preparation, sealants used, and assembly procedures are correct.
– Strategic placement of joints helps minimize corrosion risks.
– Periodic inspection can catch leaks early before failures occur.