What to do if you smell gas
If you smell gas, do not operate switches or phones inside. Leave the building and call the gas utility or 911 from a safe place. Do not try to start a unit that smells of gas.
These steps are general, and your unit's manual comes first, since models differ.
Basic startup steps
Check the power
Make sure the unit is plugged in or the breaker is on, and the display lights up.
Open the gas valve
For gas units, turn the gas valve handle so it lines up with the pipe. Check for any smell of gas.
Open the water valves
Open the cold inlet and hot outlet isolation valves, and open a hot tap to purge air.
Set the temperature
Use the controller to choose a setpoint. Many homes use a moderate setting for safety and efficiency.
What happens when you open a tap
When flow passes the minimum, the unit starts a sequence. A fan runs to clear the combustion chamber. The igniter sparks, the burner lights and the display shows a flame signal. The control board then adjusts the burner to hit the setpoint.
You may hear clicking and a fan, and you should see hot water in a few seconds. If nothing happens, check the display for a code.
If it does not start
The first place to look depends on the symptom.
| Symptom | Check | Call a plumber if |
|---|---|---|
| Display dark | Power and breaker | The breaker trips |
| Display on, no flame | Gas valve, water flow | An ignition code appears |
| Flame then shut off | Vent, scale, flow | The code repeats |
| Lukewarm water | Setpoint, flow | Flow is fine and temperature is low |
Permits, gas and the city
A new gas appliance or a changed gas line may need a permit. The City of Fountain Valley Building Division, at 10200 Slater Avenue, handles permits. Its phone is 714-593-4429, and the Permit Center portal accepts applications electronically.
Counter hours are Monday through Thursday, 7 a.m. to 6 p.m., and closed Fridays. If your tankless unit was installed recently, the installer should have handled the permit. If you are unsure, ask the Building Division.
Source type: City of Fountain Valley Building Division
Hard water and the first year
The City of Fountain Valley's 2026 report lists average hardness of 13 grains per gallon. A new tankless unit starts collecting scale from the first day. Isolation valves make yearly flushing easy, so check that your unit has them. If not, ask a plumber to add them.
Keep the manual and the installation record. A warranty may require proof of maintenance.
Common startup mistakes
Closed isolation valves, a gas valve left partly closed after work and a clogged inlet screen are common. So is expecting instant results at a low-flow tap. If the flow is below the unit's minimum, it will not fire.
Try a different tap, and open it fully.
When the unit starts then stops
A unit that lights and then shuts off after a few seconds is usually protecting itself. The cause may be low flow, a blocked vent, a dirty flame sensor or scale. Open the tap farther and see whether the unit holds. If it does, flow was the issue.
If it still shuts off, note the code and the time it takes to fail. A plumber can use that pattern to find the cause quickly.
Condensate, venting and what you may hear
High-efficiency tankless units produce condensate, a mildly acidic water that must drain away. A blocked condensate line can trip a fault code. You may also hear a fan, a click when the unit lights and a low hum while it runs. Those are normal.
Vent pipes must be intact and connected. If you see a disconnected vent or soot, turn the unit off and call a plumber. Do not run a unit with a damaged vent.
Setting the temperature
A higher setting delivers hotter water but raises scald risk and scale buildup. A moderate setting is enough for most homes. Households with young children or older adults should consider a lower limit.
Some units have a remote controller that locks the maximum. Use it. If your unit is far from the farthest tap, expect a short wait for hot water, because the pipe between them must fill first.
Keeping the unit healthy
Rinse the inlet screen once or twice a year, flush the heat exchanger on the schedule in the manual and keep the area around the unit clear. Do not store anything flammable nearby.
Write the install date and each service date on a label near the unit. It helps the next technician and supports a warranty claim.
Electrical and gas rules for tankless units
Tankless units follow the California Plumbing Code, based on the Uniform Plumbing Code (UPC), for gas and water connections and the California Electrical Code, based on the National Electrical Code (NEC), for power. A unit that does not match those rules should not be started.
Getting service
Our tankless water heater page covers installs, repairs and flushes, and the water heater installation page covers new units. We serve Fountain Valley and the neighboring city of Santa Ana.
The service areas page explains how coverage works.
Questions Fountain Valley Homeowners Ask
Most modern units use electronic ignition and have no standing pilot. Check your manual.
Common causes are no power, a closed gas valve, closed water valves or low flow.
Usually for a new install. Call the Building Division at 714-593-4429.
Follow the manual and consider scald risk. Many households choose a moderate setting.
Many units reset by cycling power. Note the error code first and follow the manual.