Code 1-11 shows up randomly and sometimes no water

Contact Paloma/Rheem customer (800-432-8373) support and ask them for the number of a local installer in your area. I had the same problem with my Paloma unit. The tech was able to diagnose the problem as the water control valve, and managed to get Rheem to pay for the cost of the part; labor was not covered because the unit was over three years old.
Hope this helps,
JZKlipper/Mike