There are multiple possible causes for this issue. Pipes leading into or out of the tank may have corroded, or the tank itself could be corroded. This requires a consultation with a plumber and likely repair or replacement work. The tank drain valve, or temperature and pressure relief valves could be leaking due to a compromised seal or fault, and these issues also require repair or replacement. Contact 180 Plumbing & Heating for help with any hot water system or leak issues you encounter.