Noritz Tankless Running but No Hot Water

The Short Answer: When water runs from a Noritz but never gets hot, check what Noritz lists for “hot water is not available”: gas and water valves fully open, the power button on, enough gas (other appliances work, propane tank not empty), the tap open far enough, and a clean inlet filter. Then look for a flashing number on the remote. That code says where the heater stopped.

Check the remote first

When a Noritz has a fault, its NRC1111 guide says the error code flashes on the remote controller along with the operation light. Photograph it. Two common codes from that guide:

If the heater lights and then goes out with a code, see Noritz code 12. For any other number, use the code list in the guide for your model, or contact Noritz. Codes and remedies aren’t always the same across models.

If the remote is dark or the unit doesn’t respond at all, start with Noritz tankless not working.

Noritz’s own checklist

Noritz’s troubleshooting section lists these questions when hot water isn’t available after opening a fixture:

1. Are the gas and water supply valves fully open? Check both at the heater. Handles should be parallel to the pipe.
2. Is the water supply cut off? Check the house main and any filter or softener bypass.
3. Is the hot water fixture open enough? The guide gives 0.5 gallons per minute as the minimum flow. Low-flow fixtures and heavy mixing can fall below it.
4. Is the gas cut off at the meter? Try the stove or another gas appliance.
5. For propane, is there enough gas in the tank?
6. Is the water drain valve filter clogged? On the NRC1111, the inlet filter is part of the water drain valve. The guide gives owner cleaning steps: close the water supply, open hot fixtures, drain, remove and brush the filter, and reinstall it.
7. Is the power button on?
8. Is the temperature setting appropriate?

Other causes

• Frozen unit or pipes. If it has been very cold, water may not flow at all, or the heater may not respond. Noritz’s guide says freeze protection doesn’t work when the power plug is unplugged, and that it doesn’t protect plumbing outside the unit.
• Reversed plumbing on a new install. Noritz lists reversed or crossed pipes when a unit doesn’t try to ignite.
• Plumbing crossover. A failed shower or mixing valve can send cold water into the hot line, so the heater sees too little flow.

What the technician will check

A technician will read the code and history, measure gas pressure at the heater while it fires, and check the igniter, flame rod and gas valve. They also confirm the flow sensor responds and check the condensate system on condensing models. If the gas line or meter can’t supply the heater and other appliances together, they recommend a supply change.

Frequently Asked Questions

Q: The heater clicks or the fan runs, but the water stays cold. What does that mean? A: It’s trying to start but failing to light or stay lit. Check the gas valve and supply, then look for a flashing code such as 11 or 12.

Q: Will flushing the heater fix no hot water? A: Not by itself. Flushing removes scale, which reduces temperature and output over time. A heater that delivers no hot water at all usually has a supply, ignition or code-related problem. If water is lukewarm rather than cold, see Noritz not hot enough.