The hot water heater on my boat started to leak, yet I could not find any leaks in the outer casing or the pipework, so I dismantled it and tested the actual heater core. This article explains the process and the unusually surprising result that might save you a lot of time if your own heater leaks.
1421 words 8 pictures. Price for this article $10
FIND THE LEAK IN A HOT WATER TANK