Dielectric union

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Old 06-30-03, 01:54 PM
curt
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Dielectric union

How do I test a dielectric union to make sure it is still working, if it can not be removed from the system, and it has water flowing through it?
 
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Old 06-30-03, 02:54 PM
T
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What do you mean test it? It either leaks or it doesn't...
All it does is prevent two incompatible materials from touching eachother.
 
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Old 06-30-03, 05:18 PM
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I think he was referring to the possibility that the union may not prevent electricity from flowing from one end to the other.

In this case, you would just use a multimeter to check for electrical continuity.

Robert
 
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Old 06-30-03, 06:03 PM
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Cool

Robert is right on.
A di-electric union is installed to prevent electrolysis corrosion between two dissimilar metals (i.e. copper and galvanized steel).
Use an ohm meter to test for continuity. Touch the leads to both ends of the di-electric union. If you don't get a reading...it's good. If you do, replace it.
Good Luck!
 
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Old 07-01-03, 06:50 AM
T
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You will still get a reading because water will conduct electricity, and what you will be measuring is the resistance of the water.
 
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Old 07-01-03, 07:07 AM
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A heating element inside a water heater, when it's dead, it will not show ohms, almost sure this will be the same when testing a union.

If the union test with no ohm resistance then the union is working.

When I test I test at the 200 setting for a water heater.

Now I just did a test with a glass of water, when the meter was set the the 200K or the 2000K setting there was a reading.

So when you test put the ohm meter on the 200 setting and not on the ???k settings.
 

Last edited by Plumber2000; 07-01-03 at 07:28 AM.
  #7  
Old 07-01-03, 10:31 AM
curt
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di-electric union

Hey guys. I found an in place tester. go to www.corrpro.com/catalog/itm_idx/121.htm to see one. thanks for your help. curt
 
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Old 07-01-03, 10:35 AM
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Originally posted by trinitro
You will still get a reading because water will conduct electricity, and what you will be measuring is the resistance of the water.

Water is not as conductive as you might think. As hard to believe as it may sound, the minimum amount of energy needed to electrocute somebody wouldn't even power a penlight. This is why taking a bath with a hair dryer in your hand is dangerous despite the fact that water is such a lousy conductor of electricity. In the case of a dielectric union, the main idea is to prevent two dissimilar metals from touching each other. If they did touch (at which point a dielectric union would become a great conductor) the iron, the copper and the water would all act like a crude battery that's been shorted out and would cause the iron to corrode much faster than it normally would.

Robert
 
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