AQUA PRO WATER HEATER ANODE RODS LEAD-FREE - ò 18% more magnesium for extended protection. ò Significantly extends the water heater tank life. The single most important factor in tank life is the condition of its anode. Aqua Pro Magnesium Anode Rods will attract the elements that cause corrosion, protecting the tank from those elements. Simply replace your MPT drain plug with the Aqua Pro Anode Rod to protect your tank. For best results the anode rod should be replaced annually. Magnesium Anode Rod for Atwood Water Heaters, Lead-Free, 4-1/2" L, 1/2" MPT. CD/1.