Installing a tankless water heater involves sizing the unit to your home’s hot water demand, then running a gas line and venting or a dedicated electrical circuit, mounting the unit, connecting the water lines, and testing the system before final inspection. If your home still relies on a bulky storage tank, you know the downsides: cold showers when the tank runs empty, wasted energy keeping water hot all day, and a unit that eats up closet space.
A tankless system solves all three by heating water only when you turn on the tap, and this guide walks through the full process, whether you’re going gas or electric.
What Is a Tankless Water Heater?
A tankless water heater heats water on demand instead of storing a tank of preheated water. Cold water passes through a heat exchanger, gets heated instantly, and flows straight to your faucet or shower. Because it only heats water when you need it, a tankless unit uses less energy than a storage tank and never runs out mid-shower.
How It Works
When you turn on a hot water tap, flow through the unit triggers the heating element or gas burner. The water heats as it passes through, and the heat turns off the moment you close the tap.
Gas vs. Electric Tankless Water Heaters
Gas units handle higher flow rates and work well for larger households, but they need a gas line, combustion air, and venting. Electric units cost less to install in most cases and skip the venting, but they draw heavily on your electrical panel.
What to Know Before Tankless Water Heater Installation
A few factors decide whether your installation is straightforward or requires major upgrades.
Sizing the Unit
Tankless units are rated in gallons per minute (GPM). A plumber calculates your home’s peak hot water demand, based on how many fixtures might run at once, and matches it to a unit that can keep up without a drop in temperature.
Fuel Type and Location Requirements
Gas units need to sit near an exterior wall for venting. Electric units need to sit close to your main electrical panel to limit wiring runs. Either way, the unit’s location affects both installation cost and layout.
Permits and Local Code Requirements
Most cities require a permit for water heater installation, along with an inspection once the work is done. Skipping this step is one of the most common reasons installations fail inspection later.
Tools and Materials You'll Need
Before you start installing, collect all the necessary materials.
Essential Tools
- Adjustable wrench
- Pipe wrench
- Pipe cutter
- Cordless drill
- Screwdrivers
- Level
- Voltage tester
- Measuring tape
- Drill bits
- Gas leak detection solution (for gas models)
Required Materials
- Tankless water heater
- Isolation valves
- Copper or PEX piping
- Pipe fittings
- Pressure relief valve
- Mounting hardware
- Vent pipe (gas models)
- Flexible gas connector (if applicable)
Step-by-Step: Tankless Water Heater Installation Process
Step 1: Size the Unit
A plumber calculates your home’s hot water demand in GPM and selects a gas or electric unit rated to handle it.
Step 2: Prepare the Site
The install location is checked for gas line capacity, electrical panel capacity, and clearance for venting or wiring, depending on the fuel type.
Step 3: Remove the Old Water Heater
Water and gas or power supply are shut off, the old tank is drained, and existing lines are disconnected.
Step 4: Mount the New Unit
The heater is secured to the wall near the water supply, with clearance for servicing and, for gas units, the vent path.
Step 5: Connect Fuel or Power
Gas units get a properly sized gas line, combustion air, and stainless steel venting. Electric units get a dedicated circuit wired directly from the panel.
Step 6: Connect Water Lines
The cold water inlet and hot water outlet are connected, and gas units also get a condensate line for high-efficiency drainage.
Step 7: Test and Inspect
The system is fired up, checked for leaks or electrical faults, set to the right temperature, and signed off at final inspection.
You can read about: How Much to Install Tankless Water Heater
Average Cost of Tankless Hot Water Heater Installation
Installation cost depends on fuel type, unit size, and how much of your existing gas, electrical, or venting setup needs upgrading. Gas installations tend to cost more upfront due to venting and gas line work. Electric installations often cost less in materials but may require a panel upgrade if your home’s current service can’t support the load. A home-specific quote is the only reliable way to know your real number, since retrofit costs vary from house to house.
DIY vs. Hiring a Professional
Why This Isn’t a DIY-Friendly Project
Tankless water heater installation involves gas lines, high-voltage electrical work, and code-required permits. This isn’t a weekend project for most homeowners, even ones comfortable with basic plumbing repairs.
Risks of Improper Installation
A mistake in gas line sizing or electrical wiring isn’t just a performance problem, it’s a safety risk. Licensed plumbers also know local code requirements, which keeps your installation from failing inspection or voiding the manufacturer’s warranty.
Maintenance After Installation
Descaling and Filter Cleaning
Clean the water inlet filter every few months to remove sediment, and descale the unit every 12 to 18 months to clear mineral buildup. Homes with hard water need more frequent descaling.
Annual Servicing
A yearly checkup catches mineral buildup and wear before it affects performance, and it keeps your warranty coverage intact.
Why Choose Derks Plumbing for Tankless Water Heater Installation
Knowing how to install tankless water heater helps homeowners visualize how a project can get accomplished – including project planning. From choosing a unit to connecting hot water lines, gas lines, or electrical wires, the whole installation works together to maintain system efficiency, performance, and safe installation.
While some experienced DIY homeowners could handle their own installations, some jobs must be done by a professional to comply with local building codes and manufacturer warranties. Proper tankless water heater installation guarantees customers years of steady, energy-saving, trouble-free use.
For a safe, efficient, and hassle-free upgrade, trust Derks Plumbing. Our licensed technicians provide expert Tankless Water Heater Installation in Eagle Rock, ensuring every system is installed to meet local building codes and deliver reliable, energy-efficient performance for years to come.
Conclusion
Tankless water heater installation, whether gas or electric, comes down to matching the right unit to your home’s hot water demand and getting the gas line, venting, or electrical work done to code. Skipping a step, from gas line sizing to permits, is what causes most installations to underperform or fail inspection. If you’re ready to move away from a storage tank, Derks Plumbing can size the right unit for your home and handle the full installation, permits included. Contact us to get a quote for your tankless water heater installation.
FAQs
How long does tankless water heater installation take?
Most installations take 4 to 8 hours, though gas units needing new venting or line upgrades can take longer.
Do I need a permit for tankless water heater installation?
Yes, most local codes require a permit and inspection for any water heater installation.
Can I convert from a tank to a tankless system?
Yes, but converting often requires upgrading gas lines, venting, or electrical capacity depending on the unit type.
How long do tankless water heaters last?
With proper maintenance, tankless units typically last 20 years or more, roughly double a standard tank.
Does gas or electric cost less to install?
Electric installations are often cheaper upfront since they skip venting, but a panel upgrade can close that gap. Gas units may cost more to install but can serve higher hot water demand.
