Bob's Insulated Horse Tank


This is an insulated horse watering tank sent in by Bob.  I think it will show a very good reduction in energy used to keep the tank water unfrozen. 


Bob reports that the horses are drinking out the tank with no problem.


Thanks very much to Bob for sending this in!



Description from Bob:

I started with a 70 gallon Rubbermaid dark plastic stock tank, then used corrugated galvanized metal panels approximately 2 feet wide, cut with shears to form siding for the stock tank. This was fit into the curled lip of the tank and held off at the bottom of the tank with sections of 2 inch thick rigid foam insulation glued to the tank with spray adhesive. (Note that the siding panels are not vertical because the tank is narrower at the bottom than the top). A cord was used to hold the panels in place while they are screwed together near what will become the bottom with sheet metal screws. Then the space between the tank and the metal was filled with expanding foam of the type available in cans at home supply stores. After the foam cures, it forms an adhesive bond so no fasteners are required to hold the metal to the tank (which would be a leak risk). A cutout was provided for access to the tank drain, and its edges were turned over for safety of horses and people.

Finally a half-cover was made using 1 inch grey non-metallic (PVC) electrical conduit as a frame with a piece of clear polycarbonate corrugated sheet screwed to it. The conduit was chosen over PVC plumbing pipe because of its UV resistance. It was formed to the required shape by bending after heating with a paint stripper hot air gun. (Metal conduit could be used if you are skilled at bending it.) A simple hinge was made with heavy gauge galvanized wire and hold downs were added with small lengths of light chain, 1/4"-20 bolts and threaded inserts in the lip of the tank. This prevents the wind or the horses from lifting the cover. Caulk and foam was used to make a fair seal of the polycarbonate to the frame and to the tank.

Insulated standoffs on Rubbermaid

After first layer of foam.


After 2nd layer of foam

After final layer of foam.

With the cover down, the horses can still access the water in the open half, but sunlight can warm the dark tank through the clear cover. It also reduces wind heat loss, evaporative heat loss, and perhaps some radiated loss at night. The covered half was placed toward the north. An electric heater was also provided, and the cover helps to discourage the horses from playing with it. In our location we were also able to place the tank against a south wall of the barn, further reducing wind loss and taking advantage of a warmer microclimate.


Finished tank with insulation
and partial lid that still
allows horses to drink.

Detail of the hinged lid.

Lessons Learned:

  1. The foam was tedious and messy to install, requiring about 8 cans of the maximum expansion type and allowing overnight curing between each can to avoid too much pressure distorting the tank. In order to reach the remote areas, extra 1/2" vinyl tubing was used to extend the nozzle, with a piece of wire taped to it as a stiffener. At one point the tubing blew off and I got foam all over my clothing and arms. So safety goggles, gloves and old clothing are a must.

  2. Next time I would consider using foam only at the top and bottom, and substituting packing peanuts or broken up pieces of rigid foam for the bulk of the insulation.

  3. I would install the corrugated metal panels in such a way as to maintain the alignment of the corrugations between panels to avoid exposed edges. This requires making curved cuts of the panels at the top and bottom, because the panels are not vertical unless one allows excessive space between the panels and the bottom of the tank.

  4. The clear half-cover gets covered with dust and bits of feed from the horses. We spray it off each time we fill the tank.
    We will see how far into winter we can go without using the heater at all. Even after we need to use it I'm sure the energy usage will be greatly reduced. Unfortunately I won't be able to quantify it since I don't have a way to monitor it at this exposed location.





October 21, 2008