Tankless Water Heater Gas Lines: Upsizing in Fullerton

Why tankless changes the gas math

A tank water heater warms a stored supply slowly with a modest burner. A gas tankless unit has no stored supply, so when a shower and a sink run at once it fires a much larger burner to heat the water as it passes through. That peak demand is what the gas line has to deliver.

In many Fullerton homes the water heater sits in a garage or exterior closet near the meter, fed by the same size pipe that was installed decades ago for a tank. That line may work for the tank and fall short for a tankless unit, especially when the furnace and range are running too.

Tank vs. tankless, from the gas line's point of view

Tank water heater

Smaller burner, runs longer
Often works on the original pipe size
Uses a conventional vent in many older homes
Must be seismically strapped in California

Gas tankless water heater

Large burner that fires only on demand
Line often needs to be upsized from the meter
Needs venting made for that unit
Total house demand may call for a SoCalGas meter review

Before you commit to tankless

The unit's maximum gas input from its spec sheet
Every other gas appliance on the same line and its rating
Distance from the meter to the water heater location
The existing pipe size at the meter and at the water heater
Whether the old vent can be reused or the unit needs its own venting
Whether a permit is needed for the water heater and the gas work
Hard water: local water is a blend of groundwater and imported water and can be hard, so ask how scale will be handled

How the gas side of a tankless install usually goes

Load and size.The contractor totals the house demand with the tankless unit included and sizes the pipe from the meter.
Meter check.If the total rises enough, SoCalGas is contacted to confirm the meter can supply it.
Permit.The gas and water heater work is permitted where the city requires it.
Run the new line.A larger line or a dedicated line from near the meter is installed, with a shutoff and sediment trap at the unit where required.
Test, connect, vent.The piping is pressure tested, the unit is connected and vented, and it is fired and checked under demand.

An illustrative example

Illustrative example. Not a real job or customer.

A single-story 1960s Fullerton home has its tank water heater in the garage next to the meter. The owners want tankless. The existing gas line is the original size and also feeds the furnace in the attic and the kitchen range.

The contractor totals the furnace, range, dryer and the tankless unit's rating.
The existing line is too small for that total, so a new dedicated line is planned from the meter outlet to the water heater location.
Because the added load is significant, the owners are told to contact SoCalGas about the meter.
A permit is pulled, the line is installed and tested, and the unit is vented as its instructions require.

The new unit gets the gas it needs at full demand without shorting the furnace or range. This is a composite example, not a record of a real job.

Common questions

Can a tankless unit run on my existing gas line?

Sometimes, if the line was generously sized. It has to be checked against the unit's rating and everything else on the line.

Does a tankless unit need seismic strapping?

Tank water heaters must be strapped in California. Wall-mounted tankless units are secured as their instructions require; ask your contractor and the city.

What drives the cost of the gas work?

Mainly the distance from the meter, whether a new line is needed versus upsizing a section, the route, any meter review, venting and permits.

General information for Fullerton, not a quote or professional advice. In an emergency, call 911.