A discussion of the
dielectric union and it's installation.
2-3 (Basic to Moderate)
Bruce W. Maki,
||This is a dielectric union.
This device electrically separates the water heater from the
It also provides a convenient way to disconnect the piping
for removal or servicing of an appliance, such as a water
heater or water softener.
Components Of A Dielectric Union:
|The big nut clamps the brass
part to the steel threaded part.
The black washer and purple insulator keep
the brass and steel parts from touching.
The brass part gets soldered to a copper pipe. The steel
part is threaded onto a piece of steel pipe.
Why is all this complicated plumbing necessary?
If you recall from high school chemistry, two dissimilar
(different) metals, when placed in an acidic solution, will create a
battery. And one metal will usually erode away as the chemical
reaction progresses. The other metal may have a buildup of new
material, which may be a chemical combination of the eroded metal
and the acid. Since virtually all domestic water is slightly acidic
or slightly basic, this electro-galvanic action can occur in
any metal plumbing system.
When copper and steel pipes are connected together directly, the
"battery" has a path for electrical current to flow. (This
current is tiny, and the voltage is not a safety hazard.)
If the current cannot flow, because there is no electrical
connection (interrupted by the plastic insulators) then the
"battery" never discharges. In theory there will always be
a small voltage between the different metals. The metals do not
Installing The Dielectric Union:
||I used a pipe wrench to install the
threaded end of the dielectric union.
||Then I took the union apart and put
a piece of copper pipe in the brass part, and soldered the
I did the soldering on a workbench, using a piece of
galvanized sheet metal (a scrap from an old section of heating
duct) as a heat shield.
||After the joint cooled down, I put
the plastic insulator on the brass part, followed by the steel
The dielectric union was then ready to use.
|I soldered the next fitting (in
this case an adapter fitting for connecting to a threaded
pipe) onto the other end of the pipe.
||The union was assembled, using a
big 15" adjustable wrench. A large pair of "Channel
Lock" pliers also works for tightening the nut.
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What's New Project
- Pipe Cutter
- Pipe Cleaning Brush
- Propane Torch
- Pipe Wrenches
- 15" Adjustable Wrench
- Dielectric Union
- Copper Pipe