Tankless water heater installation replaces the familiar storage tank with a compact, wall-mounted unit that heats water only when a tap opens. Rapid First Plumbing installs both tankless and traditional tank water heaters for Sacramento homeowners, and its plumbers assess each home before recommending a unit. A Sacramento-area plumbing company since 1974, Rapid First Plumbing handles the permit for water heater installations and services tankless units after they go in.
How a Tankless Water Heater Works
A tankless water heater, also called an on demand water heater, has no tank to keep full and hot. When you turn on a hot water tap, cold water enters the tankless unit and trips a flow sensor. The unit immediately activates its gas burner or electric heating elements, warming the water as it passes through the heat exchanger. When the tap closes, the unit shuts off.
That design changes a few things for a household:
- No standby heat loss. A tank keeps 40 or 50 gallons hot around the clock. A tankless unit only uses energy while hot water is flowing.
- Hot water that does not run out. As long as demand stays within the unit’s capacity, hot water continues for as long as you need it.
- A smaller footprint. Most tankless units mount on a wall, freeing up the floor space a tank occupied.
- A capacity limit measured in flow, not gallons. A tankless heater is sized by how many gallons per minute it can heat, so running several fixtures at once is what tests it.
Choosing Between Gas and Electric Tankless
Tankless water heaters come in gas and electric models, and the choice shapes nearly every part of the installation. The right choice depends on the utilities available, the home’s existing infrastructure, and how much hot water the household uses at once.
Gas Tankless Water Heaters
Gas tankless units burn natural gas or propane to heat water. They generally deliver more hot water per minute than electric models, which makes them a common choice for larger households and homes with several bathrooms.
Gas units come with their own installation requirements:
- Gas supply capacity. A tankless heater burns far more gas while running than a tank heater does, so the existing gas line and meter may not deliver enough. A larger gas line may be needed.
- Gas tankless units must be vented to the outdoors. Many models use dedicated vent piping that differs from the vent on an old tank heater, and the vent route has to meet clearance requirements from windows, doors, and openings.
- Condensate drainage. High-efficiency condensing models produce acidic condensate that needs a drain and, in many cases, a neutralizer.
- Electrical power. Even gas units need a standard electrical outlet to run their controls and fan.
Electric Tankless Water Heaters
Electric tankless units heat water with high-wattage elements. They need no gas line and no exhaust vent, which can simplify placement and makes them an option in homes without gas service.
The tradeoff is electrical demand. Whole-house electric tankless heaters draw a large amount of current, often requiring multiple dedicated high-amperage circuits. Before choosing one, the home’s electrical panel and service capacity need to be evaluated. If the panel cannot support the load, an electrical upgrade by a licensed electrician may be required before the plumbing installation can be completed.
Electric tankless models also have a lower flow capacity than many gas units, especially when incoming water is cold. For a smaller household, or as a point-of-use heater serving a single bathroom or kitchen, an electric unit can be a practical fit.
How Fuel Type Affects the Decision
| Factor | Gas Tankless | Electric Tankless |
| Typical flow capacity | Higher | Lower |
| Venting | Required | Not required |
| Gas line | May need upsizing | Not needed |
| Electrical | Standard outlet | Large dedicated circuits |
| Installation complexity | Venting and gas supply | Electrical capacity |
Sizing a Tankless Water Heater
Proper sizing is the most important part of tankless water heater installation. An undersized unit will deliver lukewarm water when two showers and the dishwasher run at the same time.
Two technical factors determine the correct size for your home:
- Peak flow rate. The plumber adds up the gallons per minute of the fixtures and appliances likely to run at the same time.
- Temperature rise. This is the difference between the incoming water temperature and the desired hot water temperature. The colder the incoming water, the harder the unit has to work, and the lower its effective flow rate.
A unit rated for a high flow rate at a small temperature rise may deliver noticeably less when the incoming water is colder. Rapid First Plumbing evaluates a home’s hot water demand before recommending a unit, and sizing is where that evaluation counts most.
What Tankless Water Heater Installation Involves
A complete installation typically includes:
- Removing the existing water heater, if there is one
- Mounting the new unit on an appropriate wall with required clearances
- Connecting cold-water supply and hot-water outlet piping, along with shutoff and service valves
- Making gas or electrical connections suited to the unit’s fuel type
- Installing vent piping and condensate drainage for gas models that require them
- Installing a pressure relief valve and discharge piping
- Filling the system, purging air, starting the unit, and setting the output temperature
- Testing flow and temperature at fixtures throughout the house
Isolation valves, sometimes called service valves, are worth noting. They let a plumber flush the heat exchanger later without disconnecting the unit, which makes routine maintenance far easier.
If older shutoffs, connectors, or supply lines near the installation location are corroded or leaking, that plumbing repair is best handled at the same time, while the water is already shut off.
Tankless Water Heater Replacement Versus a First-Time Conversion
Tankless water heater replacement, swapping an old tankless unit for a new one, is usually the more straightforward job. The gas line, venting, electrical circuits, and mounting location are often already in place, though they still need to be checked against the new unit’s requirements.
Converting from a tank heater to tankless for the first time involves more planning. A gas conversion may need a larger gas line and all-new venting. An electric conversion may need new circuits or a panel upgrade. The tankless unit may also go in a different spot than the old tank.
Before switching from a tank, three infrastructure checks shape the decision:
- Gas line size. Can the existing gas line and meter supply a tankless unit’s full demand, or will a larger line be needed?
- Electrical panel capacity. For electric models, does the panel have the amperage and space for the required dedicated circuits?
- Vent routing and clearances. For gas models, is there a code-compliant path for the vent to exit the house with proper clearance from windows, doors, and other openings?
Sacramento Considerations for Tankless Installation
Water Hardness and Heat Exchanger Scale
Minerals in the water can build up as scale inside a tankless heat exchanger, reducing efficiency and flow over time. Water hardness in the Sacramento area depends on where your water comes from. The City of Sacramento’s 2025 Consumer Confidence Report states that about 80 percent of the City’s water comes from the American and Sacramento rivers and about 20 percent from groundwater wells. The report lists average hardness of roughly 2 to 5 grains per gallon for the City’s two river treatment plants, while City groundwater ranges more widely, up to about 9 grains per gallon.
Homes served by other water providers, or by a well, may see different numbers. Knowing your home’s water source helps set expectations for how often the unit should be flushed and whether water treatment is worth considering.
Permits for Water Heater Installation
Rapid First Plumbing notes that state and local building agencies require a building permit when installing or replacing a water heater, and its plumbers coordinate with the appropriate agency to complete the permitting process. The agency depends on where the home is located. For example, the City of Sacramento, Sacramento County, and neighboring cities each run their own building departments. Gas line changes, new venting, and new electrical circuits can all affect the scope of what gets permitted and inspected.
Pairing Tankless Installation With Recirculation
A tankless heater produces hot water on demand, but it still has to travel through the pipes to reach a faucet. In homes where the water heater sits far from bathrooms or the kitchen, that wait can feel long. Rapid First Plumbing also installs hot water recirculation pumps, which keep hot water closer to fixtures. Some tankless models are designed to work with a recirculation system. Whether that pairing makes sense depends on the specific unit and the home’s plumbing layout.
Why Choose Rapid First Plumbing for Tankless Water Heater Installation
Experienced plumbers in Sacramento. Rapid First Plumbing has replaced thousands of water heaters across more than five decades of local service.
Tankless and tank options. The company installs both tankless and traditional tank water heaters and lists Bradford White, Rheem, and Rinnai among the brands it offers, so the recommendation can follow your home’s needs.
Permits coordinated. Rapid First Plumbing coordinates with the appropriate building agency to complete the permitting process.
Service after installation. The company services all makes and models of water heaters, including tankless units.
Licensed and screened. The company is a licensed C-36 Plumbing Contractor (California License #315742) with an A+ rating from the Better Business Bureau. Its technicians are background checked, drug screened, and DMV monitored, and they receive continuing training.
Schedule Tankless Water Heater Installation in Sacramento
If you are considering a switch to tankless or replacing an existing on demand unit, Rapid First Plumbing can evaluate your home’s gas or electrical supply, water use, and installation location before recommending a system. To get started, call Rapid First Plumbing or fill out the online service request form to arrange an in-home assessment. A plumber will review your home’s setup, explain your options, and schedule tankless water heater installation in Sacramento.
Tankless Water Heater Installation FAQs
Is a Gas or Electric Tankless Water Heater Better?
Neither gas nor electric tankless is better in every home. Gas units generally deliver higher flow rates and suit larger households, but they need venting and an adequate gas supply. Electric units need no venting or gas line but require substantial electrical capacity and typically deliver less flow. The home’s utilities, panel capacity, and hot water demand determine the better fit.
Will a Tankless Water Heater Give Me Unlimited Hot Water?
A tankless unit can supply hot water continuously as long as demand stays within its flow capacity. If more fixtures run at once than the unit can handle, the water temperature drops. Correct sizing for your household’s peak use is what makes the difference.
Do I Need a Bigger Gas Line for a Tankless Water Heater?
A gas tankless water heater often needs a larger gas line than a tank heater. Gas tankless units use much more gas while running than tank heaters, so the existing gas line or meter may not supply enough. A plumber will check the gas supply against the unit’s requirements before installation.
Can My Electrical Panel Handle an Electric Tankless Water Heater?
Many whole-house electric tankless water heaters need 200-amp electrical service and two to four dedicated double-pole breakers, typically rated 40 to 60 amps each. Homes with smaller service, or a panel without room for those circuits, may need an electrical upgrade before an electric tankless unit can be installed. The exact requirement depends on the model.
How Often Does a Tankless Water Heater Need Maintenance?
Most tankless units benefit from periodic flushing to remove mineral scale from the heat exchanger. How often depends on water hardness and usage. Homes with harder water generally need flushing more often. Service valves installed with the unit make that maintenance simpler.
How Long Does Tankless Water Heater Installation Take?
Tankless water heater installation time depends mostly on whether the home is already set up for tankless. A replacement with existing gas, venting, or electrical in place is usually quicker than a first-time conversion. Converting from a tank may involve gas line, venting, or electrical work, along with permit inspections, which extend the timeline.
Can a Tankless Water Heater Work With a Recirculation Pump?
A tankless water heater can work with a recirculation pump when the unit is designed for it or paired with compatible equipment. Rapid First Plumbing installs hot water recirculation pumps and can evaluate whether pairing one with a tankless heater makes sense for your home.
