Need advice on tank for solar water heater

[JuliaAnn]

Ok, I just had this idea and I need answers.

I have been wanting to build a batch solar water heater for some time. The kind where a tank is enclosed in a box with glazing of some sort on the cover to cause passive solar gain.

I/we (dh isn't overly excited about this project, and so while he will eventually help me, it's up to me to get the ball rolling) need to find some sort of tank. Most people use a water heater tank, and we've already looked at two at the metal recycling place and they were cracked. No landfills/dumps in this area. Got feelers out to family and friends and no one has an old water heater laying around.

So I was straightening up dh's shed and saw a couple of older propane tanks, don't know how big but maybe 25 gal. and a big one, maybe 40 gal? They have the old style valves on them and are kind of rusty on the outside. Now if we were to take the valve off the top, would I be able to see down inside with a flashlight to see if it's rusty inside? I don't even know what the inside of a propane cylinder is made of. Is it the same metal inside as out? I opened one and a tiny bit of gas came out, but then nothing, so I know it's empty.

Could one of these be used for the tank of a batch-type solar water heater? I imagine dh could cut or torch a hole in it, weld in a nipple for a valve at the bottom, etc.

Ideas?

[kreig]

I don't know about the propane tank but I made one a few years ago and got a used tank from a plumber. It was pretty cheap. By the way although I can only use mine about 7 months of the year due to the temps I love it. It works very well and was easy to make. Good luck with yours!

[TnAndy]

I wouldn't. Two problems....the "stink" they put in propane so you can smell the gas ( which is odorless otherwise ) will contaminate your water for quite a while.....you'll eventually run enough thru it to get it out, but it will take a LONG time. And the inside of the tank isn't lined like a water heater, so you'll get rusty water forever.

One way you COULD use them is to insert a coil of copper inside the tank as a heat exchanger, or wrap the outside of the tank with it.....then simply fill the inside almost full ( leave a slight airspace because air will compress as it heats, and a fluid like water will not.....making high pressure )...that way your house water never makes contact with the water in the tank.

Find a plumbing supply place, and buy a "scratch/dent" water heater.....you don't care about the jacket condition, as you're gonna strip off the jacket and insulation anyway.

Or watch Craig's list. I found some COOL stainless steel 55gal drums I intend to use for hot water storage on a solar system in my greenhouse......just be aware they probably are NOT pressure rated and don't connect to a pressurized system of any amount....or they might split wide open !

Another thing....you might go to the scrap yard and check for stainless tanks.

[wy_white_wolf]

I would not consider a propane tank for a batch tank that would be for domestic hot water.

You could keep an out out for old camp trailers that are being scrapped. Some of them have aluminum water tanks that would work great for a small batch system. I have one that 25 gallons.

You can also visit the alternative energy forum for ideas and Solar Gary's www.builditsolar.com site.

[JuliaAnn]

Yeah, been all over the builditsolar site.

Thanks guys, I appreciate the information!! BTW, I wouldn't want the water for consumption, but basically for the washing machine and maybe a tap in the washroom sink. Also, severe $$ restraints precludes me going and buying a scratch and dent water heater, or really going and buying any kind of tank at all unless it was 5 or ten bucks or something like that.

[Windy in Kansas]

For that kind of price I expect your best bet will be to use a steel barrel.

[wy_white_wolf]

I wonder how much pressure or temperature a plastic barrel could take? anyone have an idea?

[Navotifarm]

JuliaAnn, if you by some happy chance are near me in Virginia, I have a 100 gallon water heater I bought from a guy who had it as part of a big solar system. I would gladly give it to you because it's just being wasted here.
PLEASE be careful with your empty propane tanks. We had a really nice manager at the Albemarle land fill who used to cut them up for scrap. His wife is a widow now because one blew up.