@Billrw136 and
@jeff it is a timely reminder for something thats overlooked, it's one of those items that just can't be left to "The service ", like tyre pressure it's something that you need to check........................my van the HWS is used for probably 10 mths each year, it starts with tank water then progresses thru city type water to outback town water the thing is water is always passing thru , where if your parking up for months at a time you should drain your HWS, you don't need power/heating to cause the process, just water and metal sitting around doing nothing really gets things going............Someone will chime in with a more technical description I hope but like a battery sitting doing nothing chemical reactions take place and they get hungry.
Mine has Adelaide town water in it at the moment so it's probably getting a severe work out.