Corrosion concerns


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Old 01-12-19, 08:00 PM
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Corrosion concerns

John Wood water heater less than 5 years old, I change the anode rod every other year. I recently noticed corrosion at the top of the tank at both the cold water supply and hot water discharge. What's causing this and what can be done to correct it?
 
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Old 01-12-19, 08:04 PM
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My first thought would be galvanic corrosion between disimilar metals. Generally you would want to have a dielectric union between those two types of pipe. They also make braided stainless steel connections to make it easier to hook them up without a lot of exact copper connections. They are flexible and generally make it easier to connect and disconnect.
 
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Old 01-12-19, 08:16 PM
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Had to look up galvanic corrosion, but it makes sense I guess. Is it likely that the copper is flaking away and the threaded stainless post will remain more or less intact so I can couple with a braided stainless connection? Concerned that if those posts are damaged enough the water heater is useless.
 
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Old 01-12-19, 08:29 PM
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I think that in your case, the copper is probably acting as the anode and is being corroded, while the stainless steel is the cathode and is likely fine, once you brush off the corrosion.
 
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Old 01-12-19, 08:34 PM
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Hope so, fingers crossed, thanks!
 
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Old 01-13-19, 05:25 AM
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All of the pipe nipples I have seen are plated steel, not stainless. You can still have galvanic corrosion but the steel can also simply rust. While not far apart on the galvanic scale steel would be the one to corrode. So, in addition to picking up dialectric unions you might want to replace the pipe nipples depending on their condition.
 
 

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