Preheat the oven to 350 degrees F (175 degrees C). Place butter in a 9x13-inch baking dish; melt in the preheating oven.
Peel and cut sweet potato into 1/2-inch thick slices and cut in half again to make half-moon pieces. Pull each biscuit apart to make two. Wrap each biscuit around a piece of sweet potato. Arrange dumplings in the prepared baking dish.
Bring water, sugar, and pumpkin pie spice to a boil in a pan; stir until sugar is dissolved. Pour sauce over the dumplings.
Bake in the preheated oven until biscuits are browned and sweet potato is tender, 35 to 40 minutes. Baste top of biscuits with the sauce every 10 minutes or so to keep them from burning.
