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Dielectric Unions – Do You Need Them?

In this short post, we’re going to talk about di-electric unions for your water heater.

dielectric union

dielectric union

Keep in mind, when you have dissimiliar metals in your plumbing, in addition to a standard union, there exists di-electric unions which are used to separate dissimiliar metals such as copper and galvanized steel.
To avoid the damaging effects of galvanic corrosion, when two dissimiliar metals are placed in an electrically conductive solution – even tap water is conductive – they will form a battery and generate a voltage by electrolysis. When the two metals are in contact with each other, the current from one metal to the other will cause a movement of ions from one to the other, dissolving one metal and depositing it on the other. A di-electric union breaks the electric current with a plastic liner between two halves of the union, thus limiting galvanic corrosion.

For more information about galvanic corrosion, contact a local plumbing professional. A di-electric union does provide a measure of protection when using galvanized pipe. However, laboratory tests show that a simple 3 inch di-electric nipple further reduces current flow by 85 percent over the use of simply the di-electric union alone. So the next time you install a water heater, also install a di-electric nipple in addition to a di-electric union. You can buy them at your local plumbing supply store.

For more useful plumbing tips, especially for hot water heaters, visit


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