Sacrificial Anode Replacement
Two sacrificial anodes, the one on the left is totally worn after 4 years and needs urgently to be replaced. The one on the right side is a brand new replacement anode. If you don't replace the anodes every 4-5 years, your storage hot water system will then corrode from the inside. When the unit is corroded, then the only solution is to install a complete new hot water system.