Here is an illustration of my low pressure water fountain supply using a five gallon bucket as the reservoir.
This diagram connects directly to the Little giant fountain.
This is the brand we started with and like it as long as we use a (sock) pre-filter. There are other fountains that have benefits and shortcomings. Mostly, this what we started with. The unit has a small screen in the threaded connection point but it gets clogged quickly. Using the sock pre-filter mostly solves this problem.
The bucket can hang from the bail or sit over a horizontal support with a hole in it. I use both methods. In my father-in-law's tractor it hangs from the bail. In my tractors I use a milk crate with a hole cut in the bottom zip-tied to the tractor for security. If I remove the fountain by the quick dis-connect the bucket can lift out of the milk crate for dumping or maintenance.
The piece of hose allows the fountain bowl to hang level and makes swirling the fouled water out quickly and easily with one hand.
I also use this style fountain in my rain water collection system for the laying hens. I had to employ a different pre-filter than a sock.