Automatic waterers can be great to reduce the labor necessary in keeping clean, fresh water available for your horses at all times. But like water buckets and troughs, automatic waterers should still be clean and free of dirt and manure.
The benefit of water buckets or troughs over automatic waterers is when you need to measure the water intake of the horse. Measuring water intake can be especially important if you suspect a horse is sick or dehydrated. In this case, knowing the amount of water consumed by a horse is best accomplished when using a bucket or trough. As long as a horse is healthy and eating properly, water from an automatic unit would be fine and is especially handy for herds of horses on pasture. If an automatic waterer is used, it should be checked daily to make sure it is working properly, and special care should be taken to prevent freezing in cold months. If a horse goes off its feed or stops eating, this could be a result of a reduction in water intake and could be a sign that the water source is empty. If buckets are used, there should be two buckets per stall, especially in times of hot weather.