Do I need a dielectric union for copper to stainless steel?

Asked By: Mihael Obolsky | Last Updated: 29th June, 2020
Category: home and garden home appliances
4/5 (6,464 Views . 12 Votes)
The contractor did not think copper and stainless steel were dissimilar metals, and that stainless steel and copper are corrosion-resistant materials, and so a dielectric union or dielectric waterway was not required. In this case, the change was from copper or galvanized water mains to stainless steel mains.

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Considering this, can I connect stainless steel to copper?

When two dissimilar metals are directly connected together, the lesser of the two metals experience galvanic corrosion. When stainless steel is directly connected to copper, copper galvanic corrosion occurs. According to, the stainless steel plumbing pipes corrode.

Likewise, where are dielectric unions required? Dielectric union requirements. I will typically specify a dielectric union to be installed whenever dissimilar metals are joined. When copper and steel pipe are joined, the steel pipe will corrode due to the galvanic action.

Correspondingly, do I need a dielectric union for my water heater?

Dielectric Unions If either the tank nipples or the pipes are galvanized steel, however, and you are connecting them to copper, you must use a fitting called a dielectric union to make the connection. Both the hot and cold water pipes must have this fitting -- it's a code requirement.

Do you need dielectric union for copper to brass?

Re: Dielectric fittings The 2 different metals will corrode each other. You should use a galvinized nipple in the tank and a galvinized/brass dielectric union. Brass is considered compatible with steel and can serve as a dielectric fitting between copper and steel, which includes the tank.

36 Related Question Answers Found

What happens when copper touches metal?

Galvanic corrosion is caused by self-induced current created by electrical potential of two dissimilar metals in contact with an electrolyte. It can occur when two dissimilar metals (such as copper tube and steel pipe) are connected in the presence of an electrolyte.

Will stainless steel and copper cause electrolysis?

If Copper is connected to Stainless steel Type 304, then the copper will corrode to sacrifice to the stainless steel. The most serious form of galvanic corrosion occurs in plumbing or HVAC piping systems that contain both copper and steel alloys and are filled with water (an electrolyte).

What metals should not be used together?

Metals farther apart should not be used together. For example, bronze and copper can be used together; aluminum and copper should not.

Can I weld copper to stainless steel?

Soldering, Brazing, and Welding Tips. Soldering with a propane torch is the easiest way to join copper and brass. You can even use solder to join copper or brass to stainless steel, you just need the proper flux. The paste flux tends to leave tacky residue that is difficult to clean off.

Can you use stainless steel fittings on copper tubing?

Brass is for use with copper tubing, and stainless steel is for use with stainless steel tubing. For example, a ¼” compression fitting is designed to connect a section of tubing which has an OD of ¼”. When the nut (which contains the ferrules) is tightened, it compresses the ferrules onto the tubing to make the seal.

Can stainless steel be in contact with galvanized steel?

The stainless steels, including 304 and 316, are more positive than zinc and steel, so when stainless steel is in contact with galvanised steel and is wet, the zinc will corrode first, followed by the steel, while the stainless steel will be protected by this galvanic activity and will not corrode.

What happens when two different metals touch?

Galvanic Reaction Between Dissimilar Metals. This occurs when two different metals are in contact in a corrosive or conductive environment and the current flow changes. When two dissimilar metals are involved, the reaction is called galvanic corrosion.

What metals does copper react with?

Copper is the only metal apart from precious metals that will not react with water or dilute acids. It will react very slowly with oxygen.

Why do dielectric unions fail?

The unions fail whether or not the wires are installed to make continuity. If ordinary brass (copper and zinc) is in contact with water, particularly if it is chlorinated, some of the zinc can leach into the water.

Why do a dielectric union?

Dielectric Unions. Dielectric unions are used to separate two dissimilar metal pipes (such as copper pipes and galvanized steel). Purpose of dielectric unions is to prevent galvanic corrosion, which is caused by electrolysis.

When should a dielectric union be used?

The diaelectric union has the purpose of preventing corrosion that occurs between two dissimilar metals, such as copper pipe joined to galvanized pipe in a water supply system. In such circumstances the corrosion occurs at the point of contact between the two dissimilar metals.

Can you run PEX directly to water heater?

PEX can't be directly connected to a water heater. First extend a pipe 18 in. from your water heater and connect the PEX supply to the pipe.

Can you mix copper and galvanized?

Galvanized pipes should not be connected directly to copper pipes, period. The only time one can successfully replace a section of galvanized pipe with a section of copper is to make use of a dielectric union to ensure the metals do not have direct contact. Brass is an alloy of copper and nickel.

Are SharkBite fittings dielectric?

The sharkbite is all brass. The regular dielectric has the steel and copper right next to each other.

How do you remove corrosion from water heater pipes?

If you find that your copper pipe needs cleaning due to corrosion, there are a few easy steps to help you.
  1. Step 1 - Prepare. If you do not have direct access to the copper pipe joints then you will need to use a wrench or pliers to remove them to be cleaned.
  2. Step 2 - Use Vinegar and Baking Soda.
  3. Step 3 - Use Soap.

Do Rheem water heaters have dielectric nipples?

Overview. Rheem PROTECH dielectric heat traps preventing heat loss through the inlet and outlet pipes of a water heater while the heater is idle by using a flapper valve. The fittings are 3/4 in. NPT x 3/4 in.

How do I install dielectric union?

First step: Wrap several layers of pipe sealing tape over the threads of the steel pipe. Install the threaded end of dielectric union body to the steel pipe. Turn the union clockwise and tighten with a pipe wrench. Second step: Slide the union nut over the end of copper pipe with open threaded end facing out.