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Discussion Starter #1
Hello,

Need some opinions please. A 4" black pvc pipe will hold about a gallon of water per foot. Lets say you have 10' sections and connected these sections together and placed them on a roof of a house or other elevated structure so you had gravity feed hot water to wherever you needed. Can anyone see any problems this might cause? I know the system will work as far as heating the water and will do it quickly. For winter hot water could a person build a cob fireplace and place a water tank inside the flue so that when the fire is burning, the water heats up. I would build the top of the flue to where a person could take a come along to get the water tank out if needed. Any ideas or help is appreciated. Thanks

Spirit Mountain Primitive Art

Spirit
 

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Some things to keep in mind:

- Weight. I think a gallon of water weighs right at eight pounds. That's 80 pounds for a 10' length of the piping. Be sure it is properly supported.

- Variable temperature may make keeping a water supply at a certain temperature difficult, such as taking a shower.

- You will need a way to completely drain the system during winter.

- Fungus may grow on the inside of the pipes.

- Pipes may grow fragile/brittle due to ultraviolet exposure.

See if you can find a site on solar hot water heating and run your question by there.
 

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Good advice Ken gave you.
 
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There is a description of how to set up a roof top solar hot water system in the book Back to Basics.

If you have free firewood this one is good. Build a well pump house size building out of cinder blocks. Fill the walls with sand. Build a fire box vented to outside the cider building for inflow and out flow of air and exhaust. Make sure there is a doorway to feed the fire box from the outside of the cinder building. Then put a system of copper pipe inside the cinder building running into the house and tank. After you have done that fill the inside of the cinder block with sand. I am not sure if they used regular sand or green sand.

When you have this completed you start up the fire heat the sand and the water gets hot in the pipes flows out to the tank. From my understanding you don't have to keep the fire going constantly as the sand holds the heat. The guy talking about it said he heated it only every three days sometimes.

There are other technical things you may need to think through. The above is just what I remember from seeing it years ago.

obo
 

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I've seen hot water systems similar to what your envisioning. Most include a frame, with smaller pipe snaking through the frame, covered with glass. Inside of the frame is painted black. Of course, oriented towards the sun.
 

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Obo said:
There is a description of how to set up a roof top solar hot water system in the book Back to Basics.

If you have free firewood this one is good. Build a well pump house size building out of cinder blocks. Fill the walls with sand. Build a fire box vented to outside the cider building for inflow and out flow of air and exhaust. Make sure there is a doorway to feed the fire box from the outside of the cinder building. Then put a system of copper pipe inside the cinder building running into the house and tank. After you have done that fill the inside of the cinder block with sand. I am not sure if they used regular sand or green sand.

When you have this completed you start up the fire heat the sand and the water gets hot in the pipes flows out to the tank. From my understanding you don't have to keep the fire going constantly as the sand holds the heat. The guy talking about it said he heated it only every three days sometimes.

There are other technical things you may need to think through. The above is just what I remember from seeing it years ago.

obo
Obo, thanks for the pointers. I have a few questions. 1) Do you recall the material and ~size suggested for the fire box? 2) You say "fill the walls with sand" and later "fill the cinder block with sand" -- is this the same step? or do you mean that the void space in the cinder blocks and the space between the cinder block and fire box are all filled? 3) do you think the sand will get hot enough to damage solder joints? 4) do you think there is a balance in the fire box size and the amount of copper piping? 5) can you direct me to more information?
Grateful thanks,
gobug
 
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Discussion Starter #7
gobug said:
Obo, thanks for the pointers. I have a few questions. 1) Do you recall the material and ~size suggested for the fire box? 2) You say "fill the walls with sand" and later "fill the cinder block with sand" -- is this the same step? or do you mean that the void space in the cinder blocks and the space between the cinder block and fire box are all filled? 3) do you think the sand will get hot enough to damage solder joints? 4) do you think there is a balance in the fire box size and the amount of copper piping? 5) can you direct me to more information?
Grateful thanks,
gobug
1) sorry no I don't
2) Fill the walls then fill in all around the pipes too. When I think about it I am not sure it was copper pipe could have been galvanized. Was almost two decades ago.
3) I am not sure how hot it gets or how hot before solder melts.
4) I am not sure but IMO I don't think you would want to have solid copper pipe but more a coil around the fire box and on top of the fire box.
5) I am not sure as I said it was almost two decades ago. Seems like though it was in Mother Earth News. Here is a link to old Mother Earth News online articles. You may find it in there. If not contact Mother Earth News and they may know more. If you don't locate it you may have to do a trial and error on your best research on solder melting points, cubic foot of fire heat ratios and sand density retention rates.

http://www.motherearthnews.com/menarch/archive/index.html

Hope that helped. Let me know if you build it and how you did it and how it works.
 

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What Ive seen of solar roof systems. The diameter of the pipe is fairly small(like 1/2" or 3/4"). The systems circulated the water into a large storage container on the groung (usually wrapped in insulation). The smaller diamer pipe was used because the lower volume of water had time to heat up by the time it made its way through the piping. With large diameter pipe, the water must be incredabley slow to give time for the water to absorb the heat. There are many great books on the subject and even energy fairs(Oregon has one) each year.
 

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Obo said:
1) sorry no I don't
2) Fill the walls then fill in all around the pipes too. When I think about it I am not sure it was copper pipe could have been galvanized. Was almost two decades ago.
3) I am not sure how hot it gets or how hot before solder melts.
4) I am not sure but IMO I don't think you would want to have solid copper pipe but more a coil around the fire box and on top of the fire box.
5) I am not sure as I said it was almost two decades ago. Seems like though it was in Mother Earth News. Here is a link to old Mother Earth News online articles. You may find it in there. If not contact Mother Earth News and they may know more. If you don't locate it you may have to do a trial and error on your best research on solder melting points, cubic foot of fire heat ratios and sand density retention rates.

http://www.motherearthnews.com/menarch/archive/index.html

Hope that helped. Let me know if you build it and how you did it and how it works.
obo- thanks for the link. gobug
 

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The comments about the 4" vs 1/2" pipe were correct. You'd be better off with a smaller diameter pipe and more length. Black poly pipe is quite inexpensive but it won't be able to handle much pressure when hot.
 
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Discussion Starter #11
Thanks everyone for the comments. Smaller piping would be better in the climate i am in. Get hot quicker than 4'.

johnkl said:
The comments about the 4" vs 1/2" pipe were correct. You'd be better off with a smaller diameter pipe and more length. Black poly pipe is quite inexpensive but it won't be able to handle much pressure when hot.
 

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Beware of building a closed loop system without a pressure relief valve and expansion tank. Even the smallest water heater explosion can level a large house. When water flashes to steam it occupies 1700 times more space!
 
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Discussion Starter #13
Thank yo for that little tid bit of info. I didnt know that. Will take care of that little problem. Thanks again


Runners said:
Beware of building a closed loop system without a pressure relief valve and expansion tank. Even the smallest water heater explosion can level a large house. When water flashes to steam it occupies 1700 times more space!
 

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Someone mentioned that temp regulation for showers and such would be a problem but I've seen articles on rigging the solar portion as a sort of "pre-heater" that then goes into the regular water heater so that if it's not hot enough at that point for your use, the water heater doesn't have to use as much energy to get it where you want it as it would if the water was coming directly from the well. That way all you'd have to do was drain the solar part in winter if you lived in a cold climate and you'd still have hot water conventionally.
 
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Discussion Starter #15
Just a casual observation here, what do you do when you got all the water heated and don't want any more?
 

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PVC isn't used for hot water, must use CPVC. Ask plubers or suppliers or someone on here might know why. I believe the hot water chemically breaks down PVC.
 
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