Clean water is critical for your horse. And the type of hose it comes out of is as well. Only use hoses made for drinking water, NOT garden hoses. Garden hoses leach toxic chemicals into your horses drinking water. Especially when out in the sun. This is usually where most hoses at stables are, out baking in the sun.
Also, please use a filter, these RV filters are affordable and help clean up the water. You can get them and hoses at RV /camper stores and Walmart.