Received a call from a customer that I installed a gas heater for 5 months ago. He said its leaking water. Not good. Went and investigated and sure enough, really bad. I took the unit apart and found the worst chemical damage ever and the unit was only 5 months old. Here are two pictures. One of a shinny new copper heat exchanger and the other one is the one I pulled out. Notice that there is NO copper showing at all. It's all been eaten away thus leaking. 5 months old!!
Maintain your chemicals correctly and if you have a pool guy like this guy did, make sure they are doing their job.