Hello, Your tank falls into the date range when Duron tanks were being made. Does yours have a lifetime warranty? That would confirm the plastic lining. If so, the tank is likely not the source of odor, unless there is an accumulation of sediment. Cleaning out sediment in your tank would mean removing the lower element and using a shop vac to vacuum out junk… might be good to drain the tank first. 😀 Next, look at ANY place where water sits… any enlargement of the pipe. Bacteria love these places! The sulfate reducing bacteria in question are black or grey and are easy to see (and smell) on filter elements, or wherever you can get into the plumbing.