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I moved into a house with an electric hot water heater. The heater is old (11 years) but works just fine. However, the top of the tank has extensive corrosion, especially around the connections for the pressure relief valve and water in/out connections. I just flushed the tank, and there didn't appear to be any sediment (the water was at least visibly clear the whole whole time). I can't figure out how to check the anode rod, as I can't find a nut on the top of the tank (but maybe it is obscured by all the corrosion).

Do I need to worry about this, since everything is working? Or could the corrosion weaken the tank and cause it to explode? Obviously, if the tank fails, I will replace it. But, I'm wondering if its condition is a safety hazard and I need to pre-emptively take care of it.

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If it looks questionable, and is 11 years old, than it's probably at the end of its life-cycle. You could test the pressure relief valve by lifting the lever to see if water comes out the overflow. Keep a bucket under the overflow and remember it is VERY hot water! –  SteveR May 5 '12 at 20:04
    
The pressure relief valve is ok -- thanks. –  Jand May 5 '12 at 20:53
    
Can you add a photo and we maybe able to advise you further re problems that could occur or replacement advise? –  UNECS May 5 '12 at 21:54

1 Answer 1

up vote 4 down vote accepted

No matter what, it won't explode. Maybe a little bit of splat. But no boom. Ok, really, more of a squishing sound, the sound of your feet splashing through the puddle created when it fails. :)

There may well be an anode, connected to the input line. Or at least there was one, probably corroded away now.

Assuming a little water on the floor won't hurt anything, I would buy an inexpensive alarm that senses the presence of water on the floor. Its just a pair of contacts that set off a battery powered alarm when water bridges the gap. When it goes off, buy a new heater.

If some water in that area will be a problem, then the heater should be in a low pan that will catch a leak. If not, then consider a preemptive replacement, as this heater probably has only a few more years in it anyway.

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+1 as much as Mythbusters would like you to think otherwise, I believe most water heaters fail with drip, not with a boom. –  BMitch May 5 '12 at 20:47
    
With putting the heater in a pan if the leak will damage if the pan overflows consider putting in a drain from the pan (usually recommended 40mm min) and possibly a leak detecting solenoid value. These can be installed in-line and are readily available from different plumbing suppliers. Eg. Solenoid Example –  UNECS May 5 '12 at 21:57
    
@BMitch - Well, a Mythbusters water heater would most likely fail because of the large glob of high explosive they would attach, combined with a detonator. What fun is drip, drip, drip? –  user558 May 6 '12 at 2:45
    
@woodchips "no matter what it won't explode" mostly true but it's not just a myth –  UNECS May 6 '12 at 4:14
    
@woodchips - when the Mythbusters do it, they remove the TPR valve and put a heater under it without a thermostat. The result is a house destroying boom, but it takes multiple failures on an otherwise perfectly good water heater to get that result. –  BMitch May 6 '12 at 11:15

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