Is this idea for a solar water heater a decent start?

OKay. I have looked through some videos and posts about building a DIY solar water heater. One idea i was thinking was the two below. I know they are rudimentary and need more than what it is but am i correct to think that if cold water comes into copper piping at the bottom then as it heats it will over flow into the upper chamber into a second warm water tank? I know I need to have a relief value on there but what else am I missing?

Hi Celeste;  Welcome to Permies!
I would say your drawings are accurate as far as heating water expands and would flow into a second tank.
We need way more information about how you are attempting to construct your water heater.
What your needs are from that water and what style of system. A closed loop (can be dangerous) or an open tank (very safe)
Solar hot water does work. I have never built any myself but have seen systems here in the N.W. that worked all winter if the sun shined.

So we are in Baja Cal. Mexico so lots of sun. We are building on land but have an RV for now. Family of 7 but the little kids dont take showers every day for now. I was planning for the tubing some copper tubing and the cold and hot being Tenacos because they are easily available here.

thomas rubino wrote:Hi Celeste;  Welcome to Permies!
I would say your drawings are accurate as far as heating water expands and would flow into a second tank.
We need way more information about how you are attempting to construct your water heater.
What your needs are from that water and what style of system. A closed loop (can be dangerous) or an open tank (very safe)
Solar hot water does work. I have never built any myself but have seen systems here in the N.W. that worked all winter if the sun shined.

Would a closed loop still be closed if it had a relief valve?
Also the two drawings were one with the traditional smaller pipes welded into the bigger ones on the top and bottom. The second one was leaving the coil as a coil and having the water travel up that. It seems like a lot of unnessesary work to weld all the tubes into the bigger one when the coil will heat and rise the hot water too. but like i said I am just starting this idea.

Yes, even with a relief valve it is still a closed system.
You do not want to be nearby if a hot water pressure relief opens up.
Steam/hot water  is a dangerous thing , not to be taken lightly.

So your in Baja, wanting extra hot water.
Rather than copper pipe what about black poly pipe? Is it available ?
With all your sun I would think a simple sheet of plywood with black pipe looped back and forth would make a fine water heater.
Storing that water in a raised black painted tank would give adequate pressure for showers and washing.

A different option if you have wood available would be a stand alone rocket stove water heater.
Free build your own plans are available if you had interest in that.

thomas rubino wrote:Yes, even with a relief valve it is still a closed system.
You do not want to be nearby if a hot water pressure relief opens up.
Steam/hot water  is a dangerous thing , not to be taken lightly.

So your in Baja, wanting extra hot water.
Rather than copper pipe what about black poly pipe? Is it available ?
With all your sun I would think a simple sheet of plywood with black pipe looped back and forth would make a fine water heater.
Storing that water in a raised black painted tank would give adequate pressure for showers and washing.

A different option if you have wood available would be a stand alone rocket stove water heater.
Free build your own plans are available if you had interest in that.

Thank you for the idea about black poly pipe. I will have to check if this is available here. not everything my husband and I are accustomed to is available here but I can always look in San Diego. I do want to do a Rocket stove heater too but that will have to wait until we have changed over to the house and out of the RV.

Hi Celeste;   Here is a link you might enjoy looking at.  https://www.permaculturenews.org/2012/11/23/rocket-stove-hot-water/
This is Tim Barkers design rmh water heater.  It is completely safe and produces plenty of hot water.
Here is another link to our friend Matt Walkers site "Walker stoves". http://walkerstoves.com/index.html
Matt sells plans for some incredible rmh stoves, he also has just designed a rmh water heater.
Both sites are worth looking at.

I think you are over complicating the thinking.  Can you put in a single tall skinny tank possibly on a raised platform so it is higher and insulate it some?  Do away with pressurized system and adhere to kiss.  Gravity if you can get the water more than about 4 feet over your head will do.  Basing this on the portable camping shower bags.  If you can get them over your head by at least 4 feet you can get enough to take a decent shower.  Or if you have a pressurized water source like city water you can run it thru a heat exchanger in your tank but keep the hot water tank open.  Even if the tank comes to a boil it can never get the lines under pressure boiling as long as you have water in the tank.  You can do it with a single tank and a stratifier provided the tank is tall enough.  Hot water on top and cold water on the bottom.

Suggest starting with this video at 1 hour and 11 minutes in.  And watch the next 30 to 45 minutes.



It does a nice job of explaining what the tank needs to do as far as height and how to build a cheap stratifier.  Now where all you want is hot water and where you likely have a large number of sun days the tank can be much smaller.

Now your next comment is likely that it is still too expensive.  Suggest looking at this video showing how to bring the cost of the tank down.



Then if you can add a cheap black poly pipe painted even blacker plus to slightly protect it from UV and for a bit of added absorbtion and add some sort of clear cover sheet to keep more heat in you should be good.