An advantage of using 15-gallon buckets for water is they can be easily dumped, rinsed and refilled. A disadvantage is the horses can easily put their feet inside, splash out half the water and flip the things over. Which happens frequently in summer. That’s what horses do. But having no water when temperatures are over 90 degrees is unacceptable.
One way to avoid the problem is to add a 100-gallon stock tank. The drain has a 1-1/4″ pipe thread, which accepts a 1-1/4″ x 3/4″ bushing for installing a valve. The rim is high enough to deter contamination from dirty feet. You can always set it on a pallet or cinder blocks for extra protection.
When full, the tank weighs over 800 pounds, which means it’s not going anywhere until you drain it. The tank supplements but does not replace the 15-gallon buckets. You can be away for a day or two and not have to worry about water, assuming you have someone who can help with feeding and cleaning.
If you elevate the tank a few inches you can connect a garden hose to the valve and direct the old water to a suitable spot. Or you can just let it go to the ground so your horses can play in it.
The size and weight of the empty tank put it in the ‘luggable’ category. You’ll still need to clean it two to three times a week. Price was about $125 at the local feed store.