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Old 11-25-2011, 10:09 AM   #1
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Default VERY OLD hot water tanks

For those of you who have retrofitted VERY OLD hot water tanks (say 20-30+ years old) that somehow lasted throughout the years and perhaps were made long before hot water tanks were cheapened and turned into a commodity - please read:

I'm a big fan of indirect hot water tanks - for those who do not know - an indirect is a tank with a coil inside that you pump hot boiler water into at a 160-180 degrees and it heats the tank using the coil surface (essentially a built in heat exchanger) to whatever temperature you have the aquastat or sensor set at.

Anyways. A LOT of indirect HWT manufacturers use 316L stainless steel, some 316 Ti (Viessmann) for their stainless steel tanks. It is generally regarded as a very high, expensive, grade of stainless steel and 300 series stainless steels are more expensive than 400 series stainless steel due to their nickel content and nickel prices are through the roof (400 series do not contain nickel). Only one manufacturer I know of uses a 400 series stianless steel for their indirect tanks (Bradford White RTV tanks which use 444 stainless steel).

Now the reason I point this all out is the following: If you do some metallurgical reading you'll find that 300 series stainless steel are not immune to chloride (chlorine) attack. The higher the chlorine content in the water, the more degradation occurs overtime on 300 series stainless steel. Yet if you do some metallurgical reading you'll find that 400 series stainless steels are virtually immune to chloride attack.

Here is what I find even more interesting: If you look at fact sheets on the different grades of stainless steel, you'll find common uses of the various grades. Some 400 series grades are listed as being utilized for the manufacturer of hot water tanks. Now perhaps they may be talking presently, but I detect a hint of historical perspective in the mentioning of these in these fact sheets (you can find them on line - look for the A.L. sheets).

Now what I'm trying to figure out is why is there this gravitation towards 300 series stainless steel (316L, 316 Ti) in indirect manufacturing when 400 series stainless steels are cheaper and immune to chloride attack which is a common issue with domestic water, and what I'd like to know from you is how many of you have found some of these very old hot water tanks that finally failed - were they made out of stainless steel? And if so, do you know what grade they were, or perhaps can you provide some info on manufacturer, model, etc. and I'd like to research it to find out what they manufacturered some of these very old hot water tanks out of?

Indirect tanks have been around a fair amount of time, but it's only in the past 10 years that they have really started to spread like wild fire in installations in conjunctin with high efficiency boilers. So many of them haven't been around long enough to see mass failures yet - I would expect them to last at least 15 years or so but until some time passes we have yet to truly find out. I've seen a few fail but not enough to say it's a common problem.

Here is a fact sheet so you can see what I am talking about: http://www.alleghenytechnologies.com...ents/al444.pdf
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Old 11-25-2011, 06:26 PM   #2
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I've heard of them but never seen one. Didn't know they were still manufactured and I thought the coil was made of copper. Shows what I know.

When you say they fail I'm assuming you mean tank failure? How would you actually know if the coil fails?
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Old 11-25-2011, 10:41 PM   #3
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I've heard of them but never seen one. Didn't know they were still manufactured and I thought the coil was made of copper. Shows what I know.

When you say they fail I'm assuming you mean tank failure? How would you actually know if the coil fails?
If the coil fails it will overpressure the boiler causing the relief to open...

HT Products uses a cupronickel coil in the SuperStor Ultra...
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Old 11-28-2011, 10:50 PM   #4
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If the coil fails it will overpressure the boiler causing the relief to open...

HT Products uses a cupronickel coil in the SuperStor Ultra...





An alloy called 'Monel' is similar, but with monel, there is up to 67% nickel; then copper and some trace elements. Water heater tanks, I'm told, were constructed of this alloy, and therefore lasted for decades. There are still some very old W/H's around made of Monel that are still working fine.
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Old 11-28-2011, 11:08 PM   #5
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An alloy called 'Monel' is similar, but with monel, there is up to 67% nickel; then copper and some trace elements. Water heater tanks, I'm told, were constructed of this alloy, and therefore lasted for decades. There are still some very old W/H's around made of Monel that are still working fine.
And that's why you don't see Monel built water heaters any more.
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Old 11-29-2011, 12:04 AM   #6
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400 series SS is very difficult to weld. In some marine application plate heat exchangers, a liquid weld process is performed on the 436 series, which contains columbium. This property reduced stress cracking while having many properties that makes the 400 series so durable. The assembled units go through a high temp oven completing the welding process.
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Old 11-29-2011, 09:00 AM   #7
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And that's why you don't see Monel built water heaters any more.





Exactly correct. If a W/H were made of aluminum or stainless steel (the higher quality S/S, not the cheaper grade that rusts), or even a thick plastic, they'd last forever. But then companies like Rheem, AO Smith, etc. would only sell a consumer (1) W/H in that consumer's lifetime. And we all know they don't want to do that....

So instead, they mislead consumers by telling them that they are purchasing a 'glass-lined' W/H......

Now a few years back, Lochinvar was selling 'lifetime warranty' W/H's. I don't know if they still do this or not. I'm not sure if they had an extra anode rod in the tank or not.
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Old 11-29-2011, 11:37 AM   #8
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Quote:
Originally Posted by Tommy plumber View Post
Exactly correct. If a W/H were made of aluminum or stainless steel (the higher quality S/S, not the cheaper grade that rusts), or even a thick plastic, they'd last forever. But then companies like Rheem, AO Smith, etc. would only sell a consumer (1) W/H in that consumer's lifetime. And we all know they don't want to do that....

So instead, they mislead consumers by telling them that they are purchasing a 'glass-lined' W/H......

Now a few years back, Lochinvar was selling 'lifetime warranty' W/H's. I don't know if they still do this or not. I'm not sure if they had an extra anode rod in the tank or not.
Rheem now sales the Marathon WH which is a plastic tank with a life time warranty on the tank. I have not installed one but have been called several times by HO's that have picked one up at HD and wanted it installed for basically nothing. The marathon is a non-stock item at the supply house (I pay shipping) so I haven't considered picking one up.
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Old 11-29-2011, 11:41 AM   #9
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Rheem now sales the Marathon WH which is a plastic tank with a life time warranty on the tank. I have not installed one but have been called several times by HO's that have picked one up at HD and wanted it installed for basically nothing. The marathon is a non-stock item at the supply house (I pay shipping) so I haven't considered picking one up.
Yes but its an electric model only, they can be plastic-no flame
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Old 11-29-2011, 01:34 PM   #10
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Yes but its an electric model only, they can be plastic-no flame

True. I wonder though if any manufacturers are doing plastic indirect WH?
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