What can cause a pool heater to leak water?

I'm pointing at the hole in the copper tubing. This one cannot be fixed. It was damaged by improper water chemistry.

I’m pointing at the hole in the copper tubing. This one cannot be fixed. It was damaged by improper water chemistry.

Leaking heaters can sometimes be repaired in the field.
Leaking heaters can sometimes be repaired in the field.
Be sure to winterize your equipment properly!

/by