Well pump discharge faucet...

I'm in the process of doing my due-diligence on a property that has a well pump. The current owner tied into the discharge line of the pump with a tee and a standard gate-valve hose-bib-type faucet to attach a garden hose which leads to a watering trough for his horses. I don't recall seeing any other fittings in the line upstream or downstream of this tee/faucet. I didn't think much about it at the time, but is this legal? I am assuming the static pressure in this discharge line will...

Well pump discharge faucet...