Why the old line may fall short
Many Fullerton homes from the 1950s through the 1970s were piped for a tank water heater, a furnace, a range and perhaps a dryer. Each appliance has a gas input rating, and the pipes were sized to carry the total. A gas tankless heater can draw several times the gas of the tank it replaces, but only while hot water is running.
If the pipe is too small or too long for that load, pressure drops when the tankless burner and other appliances fire together. The unit may then produce lukewarm water, make noise at ignition, or show a gas supply or ignition code.
How a plumber checks capacity
- Add up the load.Every gas appliance's input rating is listed and totaled, including the proposed tankless unit at full fire.
- Measure the run.The length of pipe from the meter to the farthest appliance, and to the water heater, is measured along its actual route.
- Compare with sizing tables.The plumber compares pipe size, length and load against the sizing tables in the code and the manufacturer's requirements.
- Check pressure under load.Some plumbers also measure gas pressure at the unit with other appliances running to confirm the supply holds.
- Plan the fix.If the line falls short, options include a new dedicated line from the meter or upsizing part of the existing run.
Who handles what
| Part of the system | Usually handled by | Notes |
|---|---|---|
| Gas meter and service line to the meter | SoCalGas | Request a review if total load may exceed the meter's capacity |
| Piping from the meter outlet to appliances | Licensed plumber | Sizing, materials, pressure test and connections |
| Appliance shutoff valve and connector | Licensed plumber | Each appliance should have its own accessible shutoff |
| Permit for gas piping work | Plumber or owner | Check with the City of Fullerton for what your job requires |
Key points
- Main issue
- Burner demand at full fire, not average use
- Common fix
- New or larger line from the meter
- Meter side
- Handled through SoCalGas
- Safety
- Gas work should be pressure tested before use
Ask before gas work starts
- What total gas load did you calculate, including the new unit?
- Will the new line run from the meter, and along what route?
- Will the piping be pressure tested, and is a permit and inspection needed?
- Do we need to contact SoCalGas about the meter before installation?
Common questions
Can a tankless unit run on my existing half-inch line?
Sometimes, if the run is short and the load allows it. A plumber has to check length and total load rather than assume.
Do I have to call SoCalGas?
Only if the meter or service side may need changes. Your plumber can tell you whether total load points that way.
What symptoms suggest an undersized gas line?
Lukewarm water during heavy use, rough or loud ignition, and gas supply codes, especially when other gas appliances are running.
General information for Fullerton, not a quote or professional advice. In an emergency, call 911.