The problems that I have had in similar circumstances came from the water source to the unit (hot water line) did not have a high enough setting at the water heater thermostat. Another, the thermostat in the unit was not functioning properly, additionally, its important to make sure that the filters are cleaned daily, the lines checked to be sure there are no kinks in them that will cause pressure problems, and finally, be certain...as per manual, that your hoses are at the proper height for both drainage as well as feed.