The most efficient way to irrigate a hydroponic tower is by using a recirculating system. This involves pumping the nutrient-rich water solution from a reservoir at the base of the tower up through the pipes or channels containing the plants. As the solution reaches the top of the tower, it will flow back down, providing plants with a continuous supply of nutrients while conserving water. Using a timer and adjustable pump can help you regulate the flow of water and ensure optimal growth for your plants.