Tank or tankless
Tank
- Stores heated water, ready but limited
- Simpler like-for-like replacement
- Uses existing gas line and vent in most cases
- Takes floor space in the garage or closet
Tankless
- Heats water as it flows, so it does not run out
- Wall-mounted, saves floor space
- Often needs a larger gas line and new venting
- Needs periodic descaling with hard water
The parts of the conversion people do not expect
A gas tankless heater can draw much more gas at full output than the tank it replaces. In many 1950s to 70s North OC homes the original gas piping was sized for a modest tank, a furnace and a range, so a tankless install often includes upsizing or rerunning part of the gas line from the meter. Venting changes too, since tankless units typically use their own dedicated vent materials and terminations.
Electric tankless models can avoid gas work but may need substantial electrical capacity, which older panels may not have. Either way, an honest quote looks at the whole system, not just the unit on the wall.
Site checks before you buy
- Gas meter and pipe size from the meter to the install location
- Where the vent can terminate, with required clearances from windows and openings
- A nearby outlet for the unit's controls, if required
- A condensate drain route for condensing models
- Isolation valves for future descaling
- Space to mount it and keep it serviceable
How a conversion usually goes
- Load calculation.Estimate how many fixtures run at once and the temperature rise needed.
- Gas and vent plan.Confirm pipe sizing and a vent route. Check with SoCalGas if meter capacity is in question.
- Permit.Water heater and gas line work commonly require permits; check with your city's building department.
- Install.Remove the tank, mount the unit, run gas, water, vent and any condensate line.
- Commission.Test for gas leaks, verify combustion and venting, set temperature and show you the controls.
What drives the cost
- Gas line work
- Upsizing or rerunning pipe can be a large part of the job.
- Venting
- New vent materials and the distance to a legal termination.
- Unit type
- Condensing versus non-condensing, indoor versus outdoor models.
- Electrical
- Outlet or panel work, especially for electric tankless.
- Permits
- Gas and water heater permits; ask whether they are included.
Questions to ask installers
- Did you measure my gas line, and does it need upsizing?
- Where will the vent go, and does it meet clearance requirements?
- How often should this unit be descaled with our water?
- Who pulls the gas and water heater permits?
- What is your CSLB license number?
Common questions
Will a tankless heater give me endless hot water?
It will not run out like a tank, but it has a maximum flow rate. Running several showers and appliances at once can exceed it if the unit is undersized.
Can I put a tankless heater where my tank was?
Often, but gas pipe size and vent route decide whether that location works.
Do tankless heaters need maintenance?
Yes. With hard water, periodic descaling of the heat exchanger is part of normal care.
General information for North Orange County, not a quote or professional advice. In an emergency, call 911.