# Repurposing an electic water heater



## PJF1313 (Apr 6, 2011)

Evening Guys and Gals

 I can get a used electric water heater that is being replace due to electrical issues (3-phase heater that burned 2 legs of wiring between the inner and outer shell, that is encased with foam)  From the manufacturing date, it was built in 2000, and I know it was put into service in early 2001.  It still holds water pressure, about 65psi, and doesn't leak.

  My idea is to use it as an additional tank for my compressor.  The compressor set-up is a 2-stage, 3 h.p., oil lubed on a 50 gal. tank.  I keep the in/out set at 100/125 pi.  I was thinking that I could parallel the HWH tank so that I can increase storage, and reduce the compressor cycles.

Would this work?

P.J.


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## Beetle-Kill (Apr 6, 2011)

I can honestly say, converting a water heater into an air tank- the thought has never crossed my mind. If your shell is a min. of 11G. thick (.120") or better, and all the fittings are fully welded, it might work. If not, well... I cast my vote to not try it.


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## Dune (Apr 6, 2011)

Yep, very dangerous plan. Air tanks have a cert good for only ten years and are pressure tested to 250 psi. Could easily prove fatal.


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## PJF1313 (Apr 6, 2011)

Thanks, Beetle-Kill.  

  The only reason why it cross my mind, is that the T&P valve is factory set at 150 psi.  I don't know if I can mic. the wall, the heating elements are the "screw-in" type - it thicker in those areas to make a positive seat/seal; and the inlet/outlet/T&P/drain areas seem to be also "beefed-up" - I guess for overzealous plumbers cranking in a 3/4" fitting with a 4' wrench ;-)

  It is an A.O.Smith built commercial unit.  I don't have the model number on hand, but you gave me an idea to look at how and what they are built of and from.

  If all else fails and can't get a yes/no definite answer, I can always use it as a storage tank for my solar project that is in it's early planning stage.

P.J.


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## PJF1313 (Apr 6, 2011)

Dune - you must have replied while I was otherwise "indisposed" !

Thanks for your input, that confirms enough for me - it's a solar storage tank now.

I rather it hold water, that it is meant for, and not blow the shop to smithereens, than have a ticking bomb in there.


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## semipro (Apr 6, 2011)

I like the imaginative thinking but think it would be too risky.   My electric water heaters are/were rated for 300 PSI max with a 150 PSI working pressure.  If a tank filled with liquid breaks the result is a leak.  If a tank holding a compressed gas breaks, the results can literally be explosive.  

I just cut open a 25 year old electric water heater that I replaced because I could no longer remove the heating elements.   Amazingly, the tank was not even rusty inside.  I suspect it was a glass-lined unit.  I'm considering converting it into a heat exchanger for a solar application.


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## PJF1313 (Apr 6, 2011)

Semi.- I never did cut open one of those tanks.  

We have a bunch of water heaters at work- from on-demand to 15 lb steam exchangers; nat. gas, oil and electric.  The next time I replace one of the smaller units, I'll take a cut-off wheel to it and see what makes 'em tick!

Solar it is, or at least a storage tank for the project.

Thanks all for you input - you may have just saved a life!


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## offroadaudio (Apr 7, 2011)

You can half-bury it and cover with dirt to make a little single jump for your motocross track.


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## jimbom (Apr 8, 2011)

Water is incompressible and will not store much energy unless it is turned into steam.  Air can easily be compressed into a lethal bomb by an ordinary air compressor.  Air compressed in a water heater is a widow maker.  Don't leak test piping systems with air for the same reason.


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