Just in case you do find that the tank has busted someplace you may want to consider using a patch instead of replacing the whole water heater. I have patched gas tanks, water tanks, diesel tanks, and a variety of other things using JB weld. On a flat type os surface you should ruff up the area where you are going to place the patch and also use a little fiberglass cloth with the JB Weld. Make sure the area is clean and dry, lay down a cover coat of JB Weld, then put your fiberglass cloth on top and then apply a top coat of JB Weld. Then using a plastic spreader wipe over the area a few times using a fair amount of pressure. Make certain that your cloth stays put. Let dry overnight then you can paint it if you want. I prefer the slow curing JB to the fast stuff as it seems to hold on better.
Hope your problem is as simple as a fitting, but thouight I'd throw in a remedy just in case.
Just adding my 2¢ worth
1975 31ft Sovereign International
........Rear Bath Double Bed Model
Tow Vehicle:1999 GMC Serria SLE Classic 1500 5.7Ltr
System: Jordon 2020 Ultima Brake Controller
Hook-Up: Equalizing Hitch and Sway Bar