The electric water heater in your hot tub ensures your water will have a comfortable temperature whenever you want to use the tub. Most hot tubs pump their water through a heater tube that contains an electric heating element to heat the water as it recirculates. If there is little if any water in the heater tube, the heater is said to be dry. A dry hot tub heater may get dangerously hot and requires immediate investigation.
Newer hot baths have an electronic screen for error codes that can assist with troubleshooting. A message like “dr” or “dry” or “heater dry” is just a warning that there is no water in the heater tube. Although safety sensors are supposed to detect a dry state and shut off the heater, make sure you manually disconnect power to the heater and pump before troubleshooting the unit. First, check on the water level in the tub. If the water is low, add water to the proper level and try restarting the heater and pump.
Check for other problems that can impair or block water flow through the heater. They include blockage of the intake fitting or consumption skimmer, a dirty water filter, air trapped in the heater tube or a serious plumbing leak. Also check for improperly sealed valves that obstruct water flow through the pump.