A Noritz tankless water heater fires only when a hot tap opens, heats the water as it flows through the heat exchanger and shuts down when the tap closes. When the hot water stops, runs lukewarm or swings between hot and cold, the fault is often around the heater rather than inside it: a gas line that cannot keep up at full fire, a blocked vent, scale in the heat exchanger or a clogged inlet filter. We repair, flush and install Noritz units in Fremont, Newark and Milpitas, and we test those things before quoting a part. Fremont HVAC Masters is an independent company, not affiliated with Noritz.
Which Noritz do you have?
The model name on the rating label, on the side of the unit, tells us the family:
- EZ Series: residential models. If the far bathroom waits a long time for hot water, some EZ models can be paired with an external recirculation pump kit.
- NRC Series: condensing residential models. A second heat exchanger takes extra heat from the exhaust, which makes the exhaust cool enough for plastic vent pipe and produces acidic condensate that has to be drained, usually through a neutralizer.
- NRCP Series: condensing models with a built-in recirculation pump, so hot water reaches distant taps sooner.
- Commercial units: higher-capacity models for buildings with heavier hot-water demand.
Noritz designs its burners for low NOx emissions. Condensing or not matters most on a service call: it decides the vent material and whether there is a drain and neutralizer to check.
Common Noritz problems
| What you notice | Likely cause | What it usually takes |
|---|---|---|
| No hot water, code on the remote | Ignition or flame failure: gas supply, gas valve, igniter or flame rod | Gas pressure test at full fire, then the ignition parts |
| Water turns cold in the middle of a shower | Flow dropping below the unit’s minimum, scale, or a clogged inlet filter | Filter cleaning, flushing, a look at the fixture |
| Temperature dips when a second tap opens | Gas line or meter too small for the unit, or scale | Gas sizing check and flushing |
| Long wait for hot water at far bathrooms | Pipe length and no recirculation | NRCP model, a pump kit or a plumbing change |
| Blank display, no response | No power at the outlet, a tripped GFCI, a fuse or the board | Electrical tests before any board is ordered |
| Water dripping under the unit | Clogged condensate line or neutralizer, a leaking fitting or relief valve | Drain service or fitting repair |
| Vent code or rough, rumbling ignition | Blocked vent or air intake termination | Vent inspection and clearing |
A tankless unit’s maximum gas input is far higher than a typical tank heater’s. A gas line that served the old tank can starve the unit when two showers and the dishwasher run at once, which looks like a heater fault but is a supply problem.
Flushing and yearly care
Minerals in the water slowly coat the heat exchanger, causing reduced flow, temperature swings and, eventually, error codes. The fix is a flush: we close the isolation valves, pump a descaling solution through the heat exchanger and rinse it. The same visit cleans the inlet water filter, checks the condensate drain and neutralizer on condensing models, looks over the vent and air intake, and checks the gas connections. If the unit has no isolation valves, adding them makes every later flush quicker.
Installing a Noritz
Going from a tank to a Noritz is a new installation, not a swap:
- Gas: the line and meter are checked against the unit’s full input and upsized where needed.
- Venting: condensing NRC and NRCP models vent with plastic pipe; the old tank’s flue is no longer used.
- Condensate: condensing models need a drain path and usually a neutralizer.
- Power: the unit needs an outlet nearby.
- Recirculation: decide up front whether you want an NRCP model or a pump kit, and how hot water will return.
New installations include a free in-home estimate. We look at the gas line, the wall where the unit will hang and the vent route before you pick a model.
What to have ready
- The model and serial number from the rating label. A photo is fine.
- The error code shown on the remote controller.
- Gas type: natural gas or propane.
- Whether the house has a recirculation pump or loop.
- When the unit was installed and when it was last flushed.
Parts and warranty
We use factory certified parts only. Noritz covers the heat exchanger and the other parts for different periods, and the terms depend on the model, on residential or commercial use and on the installation, so the model, serial number and install date tell us what applies. Our repair work carries a 90-day workmanship warranty.
Local notes
In Fremont and Newark single-family homes, if the old tank sits in the garage, there is usually wall space for a tankless unit and a short vent run. In Milpitas townhomes and condos, compact closets limit the vent and drain routes, and those often decide the model more than hot-water demand does. A Noritz runs on its own controller; it is not part of your thermostat or smart HVAC setup.
Local pages: Noritz in Fremont, Newark and Milpitas. Own a Navien instead? See our Navien page.