I was hoping you’d say that. Sixteen years is pre-FVIR, so you should have no trouble examining the combustion chamber. If you like, you can photograph it and send it to me at firstname.lastname@example.org. Be sure and say it’s from leec in the subject line. I’ll tell you what I think of the condition of the heater, and from that, you can decide whether to try to extend its life or replace it.
What is he talking about? you might ask. On the left side of the Tank topics index, there are some links. Click on Water Heater Basics, and when you get to that page, click on Know-How. That will tell you how to inspect the combustion chamber.