When a Navien tankless water heater in Fremont, Newark or Milpitas stops delivering hot water, runs hot and cold, or shows an error on its display, the cause is usually on a short list: scale inside the heat exchanger, a clogged inlet filter, a gas supply that cannot keep up at full fire, a blocked vent or condensate line, a failed sensor, or recirculation settings that work against you. We repair, maintain and install Navien NPE tankless water heaters and NCB combi-boilers, and you see the price before any work begins. We are an independent service company, not affiliated with Navien.
The Navien equipment we work on
- NPE-A2 series — condensing tankless water heaters with ComfortFlow: a built-in recirculation pump and a small buffer tank, for faster hot water at the tap and fewer temperature swings.
- NPE-S2 series — the same condensing design without the built-in pump and buffer tank.
- NCB combi-boilers — one wall-hung unit that heats water for showers and taps on demand and also feeds a heating system: radiant floors, baseboard or a hydronic air handler.
- NaviLink Wi-Fi control — app control of temperature, recirculation and status.
All of them are condensing units: they take so much heat out of the exhaust that water condenses inside. That acidic condensate drains away, usually through a neutralizer, and the cooled exhaust leaves through plastic vent pipe.
Common Navien problems
| What you notice | Likely cause | What it usually takes |
|---|---|---|
| Hot water fades or swings during a shower | Scale, clogged inlet filter, short gas supply, or flow too low to keep the burner on | Flushing, filter cleaning, gas pressure check at full fire |
| No hot water and a code on the display | Ignition, flame, venting or sensor fault | Reading the code, then testing gas, ignition, vent and sensors |
| Cold burst between uses | Normal for tankless; worse with recirculation off | Recirculation settings; buffer tank on NPE-A2 |
| Water under the unit | Condensate line or neutralizer clogged, relief valve or a fitting | Finding the source before any part is changed |
| Combi: taps hot, rooms cold | Low system pressure, air in the heating loop, pump fault | Pressure check, bleeding air, pump test |
NaviLink and recirculation: the smart side
NaviLink lets you set the temperature, see the unit’s status and messages, and schedule recirculation from your phone. Recirculation keeps hot water close to the taps by running the pump, and the burner, to reheat the loop. A schedule that matches your mornings and evenings uses less gas than keeping the loop hot all day, and it is the first setting we check when a far bathroom still waits for hot water or the gas use seems high. Homes without a dedicated return line can recirculate through a crossover valve under the farthest sink; the side effect is a cold tap there that runs warm for a moment. Our smart home guides cover connected controls more broadly.
Combi-boilers: heat and hot water from one unit
An NCB combi-boiler has two loops to look after. The domestic side behaves like a tankless water heater and has the same scale and inlet filter needs. The heating side is a closed loop of water: it needs the right pressure, no trapped air and a working pump, and it pauses whenever a hot tap is open. Rooms that heat unevenly, a pressure gauge reading low or gurgling in the pipes point to the heating loop rather than the burner. A combi-boiler that leaves the house without heat on a cold night is a job for our emergency service, with phone support 24/7.
Maintenance: what a yearly visit covers
- The heat exchanger descaled through the unit’s service valves; how often depends on your water and usage.
- The cold-water inlet filter cleaned, and the condensate line and neutralizer cleared.
- Intake and exhaust terminations outside checked for nests, plants and damage.
- Gas pressure checked at full fire, and stored errors reviewed.
- On combi-boilers, loop pressure, trapped air and the heating pump checked too.
See also HVAC maintenance.
Choosing and installing a Navien
Two questions decide the model. A2 or S2: if the farthest bathroom is a long pipe run from the heater, the built-in recirculation of an NPE-A2 is worth having; with short runs an NPE-S2 is enough. Water heater or combi-boiler: a combi-boiler only makes sense with hot-water heating. Either way, the installation covers the gas line size, plastic venting, a condensate drain, a 120-volt outlet and service valves for later flushing. Every installation starts with a free in-home estimate.
What to have ready, parts and warranty
Have a photo of the rating label on the side of the unit (model and serial number), the code on the display if there is one, and the install date. We use factory certified parts only and confirm the exact part by model before quoting. A covered part keeps Navien’s parts warranty, which depends on the model, the install date and how the unit is used; labor is not included. Our repair work carries a 90-day workmanship warranty.
Local notes
Many Fremont, Newark and Milpitas homes heat with a forced-air furnace, so a Navien here is more often a tankless water heater than a combi-boiler; combi-boilers belong in homes with radiant floors or other hot-water heating. Local pages: Navien in Fremont, Newark and Milpitas. Comparing tankless brands? See Noritz.