[arcticdude]

Yes, it's possible. The potable water flows through a series of coils wrapped around the burner chamber It's completely isolated from the rest of the system.

Possibly you have a leak in that coil. Many folks have had issues there. I did not get a previous coach well winterized and had a frozen coil, resulting in a leak.

Some have repaired the coil. Some replace the unit.

Installing an external water heater is also an option.