Two concrete pipes are connected in series. The flow rate of water at 20°C through the pipes is 0.18 m³/s, with a total head loss of 18 m for both pipes. Each pipe has a length of 312.5 m and a relative roughness of 0.0035 m. Neglecting minor losses, if one pipe has a diameter of 0.30 m, determine the diameter of the other.