Water heater anode

I read that teflon tape should never be used on the threads of a water heater anode rod because it electrically insulates the anode from the tank and prevents it from protecting the tank. But I recently bought a State brand heater containing two anode rods. One rod screws in the normal way, but the other hangs from the hot water outlet by a 1" piece of plastic, and it's definitely insulated from the tank. So does this mean that the anode doesn't have to directly contact the tank?
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larry moe 'n curly wrote:

I have always used a single wrap of teflon tape around the bottom threads of the sacrificial anode rod, figuring that the top threads would provide the circuit continuity. I don't see how an electrically isolated anode would offer any electrical (current flowing) cathodic protection. Some chemical protection, maybe. Do the instructions give you a clue as to the purpose of the insulated rod?
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plate off the least noble of metals, which in a water heaters case, is zinc or some composite thereof. So I cannot imagine why it would be isolated. Try calling the manufacturer at their 800 number and ask for tech support...perhaps they can enlighten you and perhaps me too....Ross
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larry moe 'n curly wrote:

Is there any possibility that that "second piece" is somehow in the wrong place and it's really the "drop tube" for the cold water inlet? You did call it a "rod" and not a tube, so excuse me if I'm making a WAG in the wrong direction. But I too would like to know its function if it's really insulated from the tank shell.
Maybe the plastic hanger is conductive? It wouldn't have to be really low resistance to work, the current flow to an anode rod is only a few hundred microamps. And, they do make conductive plastics, like the static discharging laminates used on workbench tops to prevent electrostatic charge damage of sensitive electronic stuff.
Re the teflon tape; I ran a short series of experiments years ago to answer just that question. They showed that a reasonable wrapping of teflon tape would not electrically insulate a pipe joint made up to normal tightness. The teflon squeezed right out where there would be metal to metal contact on the flanks of the threads and stayed where it was needed to plug the "spiral leak path" between the truncated crest of the male threads and the sharp bottoms female thread.
Jeff
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Jeffry Wisnia

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Jeff Wisnia wrote:

The second anode rod looks a lot like this:
www.waterheaterrescue.com/images/ComboRodTop.jpg
Only with mine the plastic between the nipple and anode is blue instead of white. The big horizontal hole through the plastic is for letting water flow out of the heater. I measured infinity ohms between the nipple and anode (digital meter), so I don't think that the plastic is conductive.
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larry moe 'n curly wrote:

Roger that, I guess we're hopefully going to learn something new about galvanic protection, but HEY, maybe it ISN't actually an "anode" to retard galvanic corrosion?
I practically flunked chemistry, but I'm thinking maybe there's ways of inhibiting NON-galvanic corrossion of the tank by the nasty chemicals in some water supplies, by putting a "more easily corroded" material inside the tank.
Like, maybe if you've got a dish of acid it'll eat up a piece of steel you drop in it, but if you dump in some strong base the acid will get neutralized and not bother the steel as much?
I hope this thread continues until someone "in the know" educates us about that second rod.
BTW, your excellent photo shows the plastic extending through the inside the nipple right to top. That may just be to give it a "good grip" but I'm betting it's also to prevent water from touching the inside of the nipple. If the top end of an unlined steel nipple is attached to copper piping, the galvanic corrosion will be at its absolute worst inside the nipple.
The anode in the tank won't do shite to protect the nipple because the sacrificial current flow won't go very far up inside the nipple. (The same reason it's hard to get electroplating to "throw" inside the holes on a workpiece without having to stick additional anodes into the holes.)
I may have posted this here before, but at the risk of repeating myself, here's a photo of the inside of one of the galvanized steel nipple I used the last time I replaced my electric water heater. I'd dutifully bought a pair of dielectric (insulated steel/brass) unions and steel nipples and replaced the copper parts which were there before.
"Everybody" said to use dielectric unions to prolong the life of the new tank.
In less than six months both of the steel nipples were nearly clogged with clumps of rust and one had started a pinhole corroded through the "thin spot" at the root of an exposed thread.
http://home.comcast.net/~jwisnia18/jeff/nipple.html
That's when I started thinking about what I'd done and realized that because the heater tank and the house piping were both connected to ground per code, the galvanic unions were "shorted out" and (worse than) useless.
I put the all copper parts back in.
Later, I stumbled onto this document from Rheem, a major water heater manufacturer, which confirmed what I'd figured out on my own.
http://www.rheem.com/includes/resourceLibraryPDF/1221.pdf
Jeff
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Jeffry Wisnia

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larry moe 'n curly wrote:

This is getting curiousor and curiouser...
I posted the question on the forum section of the web site you swiped that photo from and received one answer already. But I'm not sure I believe it, it's too hard for me to envision how that steel sleeve he mentions isn't visible *somewhere* in that photo.
http://www.waterheaterrescue.com/phpbb/viewtopic.php?pP8#508
But I'm not sure I believe the answer, it's hard for me to believe that steel sleeve he mentions isn't visible *somewhere* in that photo, and where it contacts the metal of the nipple, but anything's posible I suppose.
Jeff
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Jeffry Wisnia

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