Getting Tanks for Solar Batch Water Heaters and Preparing Them

To build a solar batch water heater, you need a suitable water storage tank.   These can be difficult to find.   After you find one, you need a way to remove the rigid foam insulation used to

 

 

Finding a Tank

I do not know of any commercial sources for new tanks that are suitable for batch heaters for a reasonable price.  There are a few suppliers of bare tanks out there, but the ones I've seen are quite expensive -- more expensive than just buying a brand new water heater and stripping it.

 

Probably the best bet is to call around to all the local places that sell or repair water heaters.  Try to find a tank that has damage to the outer shell, but not to the tank itself.  A 2nd choice might be a used tank that is in good shape.  It may take a lot of phone calls to find a good tank. 

Here is Ron's experience:

I found the tank that I am using at the hardware store in a town near us.  We called all the plumbing shops and appliance stores and were getting pretty discouraged.  Then I talked to a guy in the plumbing department at the hardware and he had one and was more than willing to let us have it.  He wrote "Save for Ron - leaks" on it to discourage other people from taking it when he set it outside for us, it doesn't leak.  He said, "when you get it patented remember me".  A little later we got call from the secretary of a plumbing outfit that I had called earlier saying that she also had one that was basically brand new but was returned by a customer for other reasons.  It's a 40 gal. and is now resting behind our shed.  I found that the biggest supply of tanks was at the dump but they refused to let any go, some sort of regulation they say :-\

There may also be a store in the area that sells used tanks (as in a thrift or Habitat store).  If you go this route, get the best tank you can, and the price should be quite low given that you are taking some risk that the tank will have a short life.  Make sure that you can leak check the tank when you get it home, and return it right away if there is a problem.

 

Another alternative would be to buy a new electric water heating tank, and strip off the shell and insulation as described below.  This seems like a waste, and kind of expensive, but it is one way to go.

 

If you know of any other good sources, please let me know.

 

Preparing the Tank

The first thing you want to do is check the tank for leaks -- no point in putting time and effort into a leaky tank.  Then, if its a used tank, get as much of the sludge out of the tank as you can by rinsing it out with water.

 

Nearly all tanks are now insulated with foam insulation that is sprayed right onto the tank and will be well stuck to the tank.  You will have to remove this insulation without damaging the tank.

 

One person reports using a saw to make cuts in the insulation and then sanding the remaining residue off with a belt sander.  He suggests that wetting the insulation helps to loosen it.  

 

Ron reports removing the insulation this way:

The first thing I did was remove the outer metal casing which I think I remember doing by prying with a hammer and flathead screwdriver.  Then I got down to some yellowish foam insulation that was wrapped on to the core.  On that I used a hammer, wide chisel and wire brush - being careful not to hit the weld that runs down the length of the tank.  It was laborious (probably took about an hour) and I had a lot of little pieces of foam to pick up afterwards.  Then washed it, dried and painted.

 

 

 

Gary October 14, 2008