Tankless Heater Problem

Installed a S.E.T.S. tankless heater about 10 years ago. Even though it's supposed to do a whole house, I only have it connected to the shower. It has worked great for all this time until a few days ago. During a shower, I heard a loud pop and then had COLD water! Upon examination, the outlet pipe from the heater had blown apart at a 90 degree elbow about 4 inches from the heater. I didn't think it was possible for the water to get hot enough to melt the solder. Could it have been a faulty solder joint even though it has worked fine for 10 years and never leaked? Any thoughts?

You are correct in thinking water can not be heated hot enough to melt solder. The joint must have been faulty. I had a joint separate on my main supply line and shut off valve once. It wasn't 10 years old, but it was at least 3 or 4 years old.

Thanks for taking the time to reply Gary. I'll redo the joint and try the heater again.