Tankless water heaters require a minimum flow rate to be met before they activate and provide hot water. Most units have a minimum flow rate activation of .5 gallons per minute (gpm). If that minimum flow rate is not met, the heater will not activate. Make sure the fixture in question is being opened fully to the hot side. If the fixture is exceptionally low flow, it might not create enough flow to activate the heater if only partially opened.
If certain fixtures activate the heater and get hot water while others do not, there is likely a problem with the fixture not creating enough flow to activate the tankless. One possible cause could be scale buildup or other debris in the faucet reducing the flow. Make sure the shut off valves under the sink are fully opened and lastly make sure the flow rate rating on the fixture is greater than .5 gpm.
Applicable Models
- Models: ALL MODELS