If the water pump for your barn has ever shut down or frozen up, you are familiar with that panicky feeling you get when contemplating hand-carrying enough daily water for even one horse. Clearly, water is the lifeline of every horse operation.
Plumbing to your barn is installed approximately the same time as electrical lines and lies within and alongside the framing in between the walls. Specify on your building plan a location for all your water needs: your main interior hydrant, exterior faucets, laundry facilities, sink, washroom, automatic waterers inside the barn and out, and washrack. Even if you will use water buckets in stalls for now, but may install automatic stall waterers in the future, have plumbing put in place that can be easily hooked up later. Once walls are up, plumbing is tougher and costlier to change.