Using old electric water heater as tempering tank?

I will probably be purchasing a new "energy star" electric hot water heater for my house in the not too distant future. I was wondering what the issues would be (good or bad) to gut out the old one, remove the insulation and pipe it just ahead of the new one to act as a tempering tank?? I also have a wood stove in the basement for heating the house and I would place the old heater tank close to the wood stove to add heat to the tank. I'm thinking I could preheat the water in the old tank up to about 100 degrees F overnight especially. Do others here think this could be a worthwhile project to do? Thanks for any input on this! Steve
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I did that with an electric but was to lazy to strip the insulation, it still helps a bit, but I think it will sweat in summer and you will need a pan and drain hose under the tank. If you have ng or propane consider a gas tankless, i cut my bills maybe 60% by going gas tankless vs electric. One other consideration is the tank is old and will someday leak, I put in valves to I can bypass the tank without removing it.
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We went tankless but the cold water is now really, really cold. It was being tempered in the basement by the warmth of the water heater as it sat in the pipes. Unfinished part of basement is now much colder too. An advantage during the summer but disadvantage during the winter.
wrote:

I did that with an electric but was to lazy to strip the insulation, it still helps a bit, but I think it will sweat in summer and you will need a pan and drain hose under the tank. If you have ng or propane consider a gas tankless, i cut my bills maybe 60% by going gas tankless vs electric. One other consideration is the tank is old and will someday leak, I put in valves to I can bypass the tank without removing it.
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If you have ng or propane

most of this savings is by going gas.
tankless heaters have downsides like delay from flow starting till hot water arrives.
tankless must detect flow turn on burner before water starts heating.....
tankless have ;lots of downsides
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old tank might leak.........
might be better to some how plumb and circulate water around your wood stove, and send to a insulated storage tank like a solar storage tank.
someone must sell this
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I doubt if it is going to save you enough to bother.
If it did work, it would mean you would also be burning more wood or you will have a colder basement, which could convert to a cooler home.
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Joseph Meehan

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wrote:

Any savings is an investment, and what will NG cost in 20 years? maybe 4x more, so it is worth it as plumbing will last 60 yrs + and payback goes down, J.M. penny foolish as is America and most of the world.
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Maybe, but then if that tank decides to leak some night in the next 60 years and does a couple hundred dollars of damage .....
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Joseph Meehan

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I'm sure it would, with an electric water heater.

The ceiling could contain more pipes to make a greywater heat exchanger.

Nick
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Sounds good to me. An alternative is 3 or 4 10'x4" PVC pipes tucked up under the joists, if they are exposed. You might use close nipples and rubber washers as bulkhead fittings between them, with garden hose adapters at the main inlet and outlet, like this, viewed in a fixed font: --------------------------------------------------- |in out| --------------------------------------------------- --------------------------------------------------- |out in| --------------------------------------------------- --------------------------------------------------- |in out| --------------------------------------------------- --------------------------------------------------- |out in| ---------------------------------------------------
The main outlet could connect to the water heater drain.
The pipes would hold about 220 pounds (26 gallons) of water with 40 ft^2 of surface. In slow-moving air with a 1.5 Btu/h-F film conductance, RC = 220/(40x1.5) = 3.7 hours. After 4 hours in 100 F air, water would warm from 55 to 100+(55-100)e^(-4h/3.7h) = 85 F. A foil wrap around the pipes and insulation above them would help.
Nick
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On Mar 12, 4:54pm, snipped-for-privacy@ece.villanova.edu wrote:

Thanks! That sounds like a good plan also. But my ceiling joists are pretty full or covered with ductwork and stuff. Especially over my wood stove which would be the best place for something like this. And I wonder about a dripping of condensate problem in the summer?? With my wood stove going strong in the winter months, my basement near the wood stove is easilly close to 90 - 100 degrees F and I don't think it would make me have to burn any more wood because of it if I put my old hot water heater tank (which is fiberglass vintage 1978) close to the wood stove. Do you think it would cause a loss of or problem with water pressure? I have a well system with 35 - 45 psi. Thanks again! Steve
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In summer heat is free, as in the water will come in at 50f and heat free to 70f, a big savings, PVC wont transfer heat like Copper, Copper will absorbe summer heat more efficiently Do it but Copper is best.
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Thanks! I think I will do this. My plumbing is mostly copper already so I plan to stay with it. If I can save up to 5 kwh/day (about 30% less on time) with this @ .10 / kwh, it could be a savings of up to $180 / year. Enough to payback the new heater! Steve
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Not in the basement :-)

No, given the much larger limiting airfilm resistance.
Nick
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Warm air rises, so the pipes might work well anywhere in the ceiling. I removed most of the wooden cross blocking in the basement ceiling of my neighbor's house and tucked 60 50-pound capped 4"x10" thinwall PVC pipes between the joists with 1x3s beneath to add 3K Btu/F to the house thermal mass and make the basement woodstove heat last longer. A few more thickwall pipes to make a tempering tank would be useful.

You might catch any condensation with a piece of plastic stapled beneath. If it happens a lot, the basement may need airsealing or dehumidification.
Nick
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My brother did something like this several years ago. Two old non functional hot water heaters in front of the working one. They are in his garage. He doesnt have a freeze problem where he lives but he still bypasses them in the winter, about 3 months. cut his LP gas usage by a third.
Jimmie
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