I live in central Iowa and it's 19' outside.   I used to try a do what you are doing, but with stock tanks.   Be careful the horses don't pull the heater out.  15 gallions isn't much cover.  I now have a Nelson waterer and LOVE it.  It has a self container heater, and the lid spins off and you can pull the bowl out and clean it.   I don't have to worry about it at all.  I do check it daily, but I also check on my mares every day too.  Be aware they are exspensive, but I felt it was worth it.  I also have a very large bucket type waterer with a built in heater in the bottom.  Works great.  That's all I used last winter before I got the Neson Waterer.  I think I got it at a tractor supply or farm store.  Can't remember the name.

My friend has one of those Bar Bar A waterers.  She hates it. 

Ditto on the Nelson Waterer. I have 2, and love them! Yes, the intial cost is high compared to others, but they are sturdy, and easy to clean. I have had them for about 8 years, and only replaced a thermostat on one of them once. Friends have other brands that pay $100 for thermostats on a much more frequent basis. I will replace the thermostat on the one that has never had the thermostat replaced soon, as a precaution, as the last one went out in the worst part of winter, of course!

Brenda

I have had the Bar Bar A for 9 years. It was in the 13* last night and the waterer worked fine this morning. It's supposed to drop to 5* tonight and I expect it will still work just fine tomorrow, It's been down to -10 around here and it still works.

But my horses still prefer to just drink out of the tank. I have a 100 gallon tank next to the waterer. I break the ice off it each morning and make sure it is full of water and thats where the horses drink. I suppose I should force them to use the other.

Around here the earth 5' down remains 52*. Since that's where the Bar Bar A valve is located, I'm pretty sure the water that come up is 52*. I'll have to take a temp reading and see. Since it takes 2-3 seconds for the water to fill the bowl, the horses prefer the instant gratification of water in the tank, even if it's 38*.

I have no power near the water source.  So I had to use something that doesn't require power. And the Bar bar A meets that requirement. Talking to the inventor, He told me to just remove the tank and the horses would just adapt to the automatic watering. But since I've had the tanks, I always just left them.

Ditto on the Ritchie automatic waterers,everyone that I know that has one loves it.Never freezes.Of course,we are in NE Arkansas,so,the temps here do not reach that low.They do make them with heaters for colder climates.Our big concern here is water evaporating and the horses running low in summer heat,so,that's why the Ritchie is so popular.

"What a nightmare it is keeping water from freezing. I remember when I was much, much younger. My dad would trudge up to the pond on cold mornings and chop a hole through the ice with a pick axe for the cattle to drink before it refroze. Now we have higher expectations and more technology and it's still not easy"

Not trying for a pity party here by any means but what you said reminded me of the winter I was in chemo treatment for breast cancer.It was a cold hard winter,and,I recall having to break the ice in the water tanks with a sledge hammer,take a pitchfork,and,heave the thick ice blocks out.That nearly killed me!

The Bar Bar A still works. It's probably 10 years old, Maybe 12 years and the only maintenance I've ever done was to replace the paddle once. Horses broke it off trying to chew on it. Ireplaced the original black pastic paddle with the newer metal paddle.

No electricity, Never freezes.

I have no idea how much water they drink out of it. I don't have any kind of consumption meter.

The original inventor of the product lived 5-6 miles away and built them in his garage. I bought mine from him. The company has been bought and moved to new city and is much commercialized than when I bought mine.

Day time highs yesterday were around 17 and it was supposed to have dropped to 0* last night

 I live in Northern Michigan it is about 18 degrees right now.  I got a Nelson several years ago and would NOT get another. The company is no help at all if "they" screw up..  I ordered the type that fits in a cement water line, 6 feet down in the ground then the cememt part sticks up, When they sent the unit they did not include the instruction book,  there was a ledger sized piece of paper with basic instructions but no 26 page manual included..I unpacked the box myself and I worked in a store room once so I am very very very familiar with looking for pack slips, and paperwork when unpacking.  I actually called Nelson after unpacking it and asked if those instructions were all my contractor needed -and I was told on the phone that "MY unit was shipped complete and what ever was in the box was what I purchased"  I hired a licensed insured well driller/plumber to install it the total bill was around $1,000 for installation.  I had nothing but problems with it freezing the first two winters, when i sent pictured into Nelson they said It wasn't installed according to insturctions on page  I said I didn't get a manual they basickly said tough s it.  It cost me another $400 to have another heat tape put down in the hole,  i got the unit thinking insted of using a 1,000 watts the nelson only uses 200 watts but now I have an additional heat tape with 200 extra watts.  I built a three sided wall around it and bank it up with snow and yes you have to check it every day.  Have you thought about putting a timer on a type of water heater for you tanks?