Thanks for your advice. It is not "RARE" when I am the jerk that cut off the threads a year ago when I built the fountain! This was a 16" long threaded nipple, which threads to a coupling below which is sched 40 PVC. I don't remember whether I used pvc or brass for the coupling. The coupling is embedded in the 6" thick concrete pour which is the base of the fountain. I cut off the threads because I thought the control unit for the autofill would be separate from the pipe, and water would then rise from the pipe controlled by a separate sensor. Someone clued me in to the Hudson valve, which is self-regulating and threads to the pipe itself.
If I attempt to thread the brass, if I don't apply perfect counter-torque with a pipe wrence I could tighten the pipe and snap the fitting, or rotate the pipe slightly and break the thin layer of epoxy sealer that lines the fountain. This would allow water to leak out the fountain and would be a pain to correct, since there is tile above the epoxy layer.
The brass nipple is 1.06" in diameter. I don't believe there are compression fittings for this size pipe. I found a 9" long brass fitting at Home Depot that fits loosely into the nipple, that might allow an epoxy seal, but I don't know if that would hold. Can you solder brass to brass if the fit is loose?