my black pipe solar water heater
 

I had a bunch of 1 inch black pipe laying around so I thought I would make something fun for the kids to shower up with outside cause Im sick of bending over the tub to wash hair. Its more fun to hose them off, only problem is water gets really hot and need to let it cool down first.

http://i56.tinypic.com/r1j710.jpg

I bought an old water heater for 25 bucks and mounted this whole thing on top of my little flatbed trailer so I could pull it round the yard to where I needed it. At first I tried to make it a full thermosyphon set up but thermosyphon was way to slow and most of the heat was wasted. I ened up using a differential thermal controller and a 120 volt pump to force it into the tank when it should. THen I relaized that my coil has over 30 gallons of water in it alone(more than enough) so I disconnected the water heater and just used the water in the hose. At 8 foot diameter, this thing is picking up about 3000 watts of thermal energy, It can recoup heat from 55 to 120 in about 35 minutes so I think thats pretty good.

Heres the differential controller I initially built using arduino to turn pump on etc. let me know if anybody needs code.

http://i53.tinypic.com/11ajyw5.jpg

Very cool setup. I would imagine it gets QUITE hot! I like the arduino setup too. Its a bit fancier than mine with the LCD display. :)

BTW, welcome to the site.

I need to actually solder up the prototype board for it and cut some well shaped holes in a nice 8" otterbox(waterproof) and make it look legit. Also will be adding a ethernet card so I can monitor and datalog over the network, and last but not least a 4 or 6 button keyboard so I can set Temps from the unit and not the pc. Should be a pretty sweet setup when done, I was thinking about selling these things, being that online for a comp setup they are running like 600 bucks for all these features! thats nuts.

totally post the code. I'm curious about the LCD display. Also what did you use for the relays, was it a prebuilt sheild or something you put together?

I'll post the code after I make the next few updates. The Lbraries I use are super simple. After the wiring is correct, its basically "lcd.write....". Relay board I bought complete.

"only problem is water gets really hot and need to let it cool down first."

How about installing a mixing valve? Might make it safer to use and they don't cost too much off Ebay..
ZURN WILKINS THERMOSTATIC MIXING VALVE 1/2" ZW1070C | eBay

Neat idea and im sure your kids love it too.

Any idea what the temperature limit is on that black pipe?

not really sure
 

But I would think you could practically run 150 degree water through there without incident. I think the only thing to watch out for , (in all things) is age. Not sure how long the black pipe can hold up under direct sun. Should be at least 3 or 4 years I would think.

I chatted with a guy online who used the black pipe you are using, and he said its on its 6th year without problems . Ive heard of a spray you can apply that stops UV getting thru...you may want to do a google for it.