A tankless hot water heater is a space-saving alternative to a traditional water heater. Cleaning them will need to be done occasionally to prevent and flush-lime deposits out of the system. This is a relatively simple job for those who have some DIY experience.
Step 1 - Preparation
You want to make sure you have all the water valves turned off before you start. Disconnect the inlet hose using the wrench and attach a garden hose to it. The other end of the garden hose should attach to the outlet on the water pump. Now remove the outlet hose on the water heater and attach another garden hose to it. The other end will need to be placed in the bucket. The last garden hose will attach to the inlet on the pump with the other end in the bucket. Place at least 2 gallons of vinegar in this bucket.
Step 2 - Start Pumping
Turn on the water pump and allow it to pull the vinegar from the bucket. It will push this through the tankless heater. Once it's cycled through the pump it will drain back out in to the bucket.
Step 3 - Finishing Up
Once you're done with this you can begin to assemble the heater again. Run hot water through the system for about 15 minutes. You can do this by turning on the hot water in a nearby sink. This will pull the hot water through the system and act as a final rinse.