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Old 06-05-2013, 11:27 AM   #1
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Tempering Tank


My water/waste system is well/septic. The well is a deep well, at approximately 250 deep. The water coming out of the ground is at around 55 degrees F.

My grandson (10) completes fourth grade in a few days, and as a summer project I have been thinking of installing a tempering tank to elevate the temperature of the ground water before it gets to my hot water heater. I intend to go over to our landfill, where scads of used Hot water heaters are brought in every day for recycling, pick up one that looks good, probably an electric, scope the inside to make sure I did not get a lemon, and basically hook it up in series with my HWH with bypass shut off valves for the winter. I will remove the outer shell and insulation, paint the tank flat black and basically stand it outside where the sun can heat up the water in the tank. I will install a new PRV on the tank just in case the temperature rises too much. The lines to and from the tank will be installed so that they can be bled down completely in the winter time.

It is fairly amazing to me that considering how many wells we have in this country, and the way people go on about abusing our natural resources, not even to mention about abusing our wallets, something like this is not required by code.

I guess making sure the tank and lines do not freeze, and making sure the tank is sanitized before use would be way beyond the capabilities of most people.

Does anyone see and glaring pitfalls in this approach? It makes a lot of sense to me as showers are taken in my house in the evening after work, when the water in the tempering tank would sit in the sun all day.

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Last edited by jagans; 06-05-2013 at 11:29 AM.
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Old 06-05-2013, 11:32 AM   #2
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Originally Posted by jagans View Post
... been thinking of installing a tempering tank to elevate the temperature of the ground water before it gets to my hot water heater.

Does anyone see and glaring pitfalls in this approach?
How about just extra pipe?
A length of 3" PVC on the manifold...
two halves installed vertically...

But if you're gonna have a tank... buy a new one.

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Old 06-05-2013, 11:56 AM   #3
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Quote:
Originally Posted by TarheelTerp View Post
How about just extra pipe?
A length of 3" PVC on the manifold...
two halves installed vertically...

But if you're gonna have a tank... buy a new one.
If by a length you mean 20 feet, that would only yield 1/2 cubic foot of water, then there is the pressure issue.

As far as a new tank goes, they are expensive. I could be wrong but I bet a lot of electrics are thrown out just because the thermostats went bad. I could be wrong on that one, but I doubt it. We shall see, you may be right.

Thanks TT
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Old 06-05-2013, 12:12 PM   #4
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Sounds pretty smart/clever/economical to me.... guess any drawback would be aesthetic and finding the best sun exposure.... and for some people the switching over maintence in fall and spring.
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Old 06-05-2013, 12:26 PM   #5
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Originally Posted by jagans View Post
If by a length you mean 20 feet
X linear feet of 3" or 4" pipe will hold a LOT of water.
How much do you really need?
dia squared x 3.1416 x length x 7.48g/cf =


Quote:
As far as a new tank goes, they are expensive.
Not a WH tank... an anything made of PVC or ABS tank.
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Old 06-05-2013, 12:52 PM   #6
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I think you would be more efficient with a closed solar system with a heat exchange. With your design, you are introducing cold well water to the tempered water thereby lowering the temperature. You need a way to keep the solar storage loop warm and not drop temperature. In the attached image, perhaps use your "tank" as the solar panels and add a 2nd solar exchange tank inside... just thinking out loud
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Tempering Tank-jababasicsolarhotwatersystem.jpg  
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Old 06-05-2013, 01:29 PM   #7
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Quote:
Originally Posted by TarheelTerp View Post
X linear feet of 3" or 4" pipe will hold a LOT of water.
How much do you really need?
dia squared x 3.1416 x length x 7.48g/cf =



Not a WH tank... an anything made of PVC or ABS tank.
TT... Think it works out...

Volume per running foot (assuming 4"ID)

((Radious squared x 3.14 x12/ 1728)(7.48)= about .65 gal/running foot

So, a 40 gal tempering would require about 60 feet of 4"


EDIT: But I would suppose you would get alot more surface area for heat transfer.

I took out an old (early 80's) closed system in a home I redid, as EPlumb notes... certainly more efficient... certainly more expensive.

It was deteriorated so I never really knew how well it worked. (They even had a "heater loop" installed in an upstairs bathroom... which did not have a bypass, so I guess in summer they had a very warm bathroom if it worked at all.)

The real drawback for me, besides the system was leaking and pumps controllers were shot, was the utility room where it was installed looked like a submarine... scarry to buyers... I got $500 for the 3 4'x10' roof panels and several hundred for the copper I pulled out of the house.

EDIT2: It would be interesting to know what the payback on that system would be.... I know it was expensive install, and I can't imagine that it could save enough heating water, to make it economically viable. I suspect it was put in during the 80's energy scare, maybe when NG hit that $12/mcf for a short period.
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Old 06-05-2013, 01:42 PM   #8
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[QUOTE=MTN REMODEL LLC;1195694]
But does he need 40 gallons?
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Old 06-05-2013, 02:01 PM   #9
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[QUOTE=TarheelTerp;1195701]
Quote:
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But does he need 40 gallons?
No idea... I guess the reason I liked Jags thought, was that he would be getting some (how well a water heater tank absorbs heat is an unknown) heat gain, at virtually no hard cost to him.... can of black paint, some pipe/valves.
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Old 06-05-2013, 05:23 PM   #10
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Im not going high tech, here. Im sure most of you guys have left a crowbar or something lying in the sun for a while and when you picked it up, you had to drop it it was so hot.

Now consider a 50 gallon tank painted flat black that refills at around 7:00 PM with 55 degree water. That water sits in that tank at ambient temperature which is from 70 to 95 degrees overnight and all day. Then add solar radiation on flat black paint. Its got to make a heck of a difference in the water temperature entering the HWH, dont you think?
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Old 06-05-2013, 06:09 PM   #11
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I personally think your plan isn't worth the effort for the results you would achieve. There's a reason virtually nobody does what you want to do, and that's because it's a waste of time. A tank of water is a whole lot harder to heat than a crowbar. Best case, with an ambient temperature of 95 degrees all day, you might see a 4- or 5-degree rise in water temperature.
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Old 06-05-2013, 06:22 PM   #12
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OK- you got me curious I found a PDF from the 1980's. Your plan is sound and has been done before- they show some refinements. Enjoy
http://ir.library.oregonstate.edu/xm...047?sequence=1
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Old 06-05-2013, 07:17 PM   #13
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Originally Posted by md2lgyk View Post
I personally think your plan isn't worth the effort for the results you would achieve. There's a reason virtually nobody does what you want to do, and that's because it's a waste of time. A tank of water is a whole lot harder to heat than a crowbar. Best case, with an ambient temperature of 95 degrees all day, you might see a 4- or 5-degree rise in water temperature.
Really? I am amazed.
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Old 06-05-2013, 07:29 PM   #14
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Thanks E, I was able to download the PDF. For some reason, I was under the impression that I would save a lot more than 30% of my annual water heating cost, and the amount they are talking about saving is not all that much. I am surprised.
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Old 06-05-2013, 07:56 PM   #15
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Thanks E, I was able to download the PDF. For some reason, I was under the impression that I would save a lot more than 30% of my annual water heating cost, and the amount they are talking about saving is not all that much. I am surprised.
I agree to an extent. The report is 30ish years old. Who knows how energy prices now compare and I presume the testing was done in Oregon- that's the state that people rust, not tan. So the measurable sunlight may be less than your area. Also, today's heaters are more efficient so that's a plus.

But for a project to do with your Grandson, it may be worth it's weight in gold!
BTW- I googled homemade solar water heater to find that report

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