Tired of running out of hot water mid-shower? A tankless water heater gives you endless hot water and cuts your energy bills by up to 30%. Here’s the straight answer: installing a tankless water heater takes 6-8 hours and requires shutting off utilities, removing your old unit, mounting the new heater, connecting gas or electric lines, hooking up water pipes, and installing proper venting.
This guide walks you through every step of how to install tankless water heater. You’ll learn what tools you need, common mistakes that cause problems, and when to call a professional. Let’s get your new system running.
What Is a Tankless Water Heater?
A tankless water heater heats water on demand instead of storing hot water in a tank. When you turn on a hot water tap, cold water flows through a pipe into the unit. A gas burner or electric element heats the water instantly as it passes through.These units are also called on-demand or instant water heaters. They’re compact, about the size of a suitcase, and mount on your wall. Most tankless systems last 20+ years, which is twice as long as traditional tank heaters.
The main types are gas-powered and electric. Gas units heat water faster and work better for larger homes. Electric models cost less upfront but may need electrical upgrades to handle the power load.
Benefits of a Tankless Water Heater
Switching to tankless saves money and space. These systems use 24-34% less energy than tank heaters in homes that use 41 gallons or less of hot water daily. For homes using around 86 gallons per day, the savings drop to 8-14%, but that’s still a win.
You’ll never run out of hot water again. Tankless units provide 2-5 gallons per minute continuously. Gas models deliver higher flow rates than electric ones.
Space savings matter too. Tank heaters take up 16 square feet of floor space. A tankless unit mounts on the wall and uses less than 2 square feet. That frees up room in your utility closet or basement.
The lifespan is another big plus. Tankless water heaters run for 20+ years with proper maintenance. Traditional tanks last only 10-15 years before they rust out and leak.
Energy Star certified models qualify for federal tax credits and local rebates. Check the Database of State Incentives for Renewables & Efficiency to find savings in your area.
Tools and Materials Needed
Get everything ready before you start the tankless water heater installation. Missing a part halfway through turns a one-day job into a weekend nightmare.
Basic Tools:
- Pipe wrench and adjustable wrench
- Tube cutter or hacksaw
- Drill with bits
- Level
- Screwdrivers (flathead and Phillips)
- Tape measure
- Teflon tape
- Pipe thread compound
Materials You’ll Need:
- Tankless water heater unit
- Gas line parts (if gas model) or electrical cable (if electric)
- Water supply lines and fittings
- Venting materials (for gas units)
- Pressure relief valve
- Shut-off valves
- Wall mounting brackets
- Sediment filter
Safety Gear:
- Work gloves
- Safety glasses
- Dust mask
Gas installations need a gas line kit with proper connectors. Never use flexible gas lines not rated for water heater use. Electric models need the right gauge wire based on amperage, usually 8-gauge or larger.
Check your local building codes before buying materials. Some areas require specific venting types or earthquake straps. Getting this wrong means failing inspection.
Step-by-Step Guide: How to Install a Tankless Water Heater
1. Turn Off Utilities and Drain the Old System
Safety comes first. Turn off the gas supply at the main valve if you have a gas heater. Flip the breaker for electric units. Next, shut off the main water supply to your house.
Open a hot water faucet on the lowest floor to release pressure. Attach a garden hose to the drain valve on your old tank heater. Run the hose outside or to a floor drain. Open the drain valve and let the tank empty completely. This takes 20-30 minutes for a 40-50 gallon tank.
2. Remove Your Old Water Heater
Disconnect the gas line using two pipe wrenches. One holds the pipe steady while the other loosens the connection. For electric heaters, disconnect the wires after confirming power is off with a voltage tester.
Cut the water pipes about 6 inches from where they connect to the old heater. This gives you room to work with when connecting the new unit. Remove any mounting straps or brackets, then carefully move the old tank out of the way.
3. Prepare the Installation Location
Pick a spot close to existing gas and water lines. The area needs adequate clearance, usually 6 inches on sides and 24 inches in front for maintenance. Gas units need access to outside walls for venting.
Mount the wall bracket using the template that comes with your heater. Check it with a level. The unit must sit perfectly straight or it won’t work right. Use lag bolts to secure the bracket to wall studs, not just drywall.
4. Install Gas Lines or Electrical Connections
Gas tankless water heater setup requires a licensed plumber or gas fitter in most areas. The gas line must be sized correctly based on BTU requirements and pipe length. Under-sized gas lines starve the heater and cause performance problems.
Run black iron pipe or approved flexible gas connector from the gas supply to the heater inlet. Apply pipe thread compound to male threads only. Tighten connections firmly but don’t overtighten and crack the fittings.
For electric models, run cable from the breaker panel to the heater location. Most units need a dedicated 40-60 amp circuit. Connect wires according to the wiring diagram in your manual. Cap unused wires with wire nuts and secure everything in the junction box.
5. Connect Water Supply Lines
Install shut-off valves on both hot and cold water lines. These let you service the heater without draining your whole house. Use copper, PEX, or CPVC pipe based on local code requirements.
Connect the cold water inlet first. Many systems require a sediment filter before the water enters the heater. Hard water and debris damage the heat exchanger over time.
Attach the hot water outlet pipe next. Use proper support brackets every 6 feet to prevent pipe stress. All connections need Teflon tape or pipe compound to prevent leaks.
Add the pressure relief valve to the designated port. Run a discharge pipe from this valve to 6 inches above the floor or outside. This safety valve releases pressure if something goes wrong.
6. Install Venting for Gas Units
Tankless water heater venting is critical for safety. Gas units produce combustion gases that must vent outside. Most modern tankless heaters use sealed combustion with intake and exhaust pipes.
Direct vent systems pull air from outside and exhaust back outside through concentric pipes. Power vent models use a fan to push exhaust gases out. Both styles work well but require different installation approaches.
Follow the manufacturer’s specs exactly for vent pipe size, length, and number of elbows allowed. Use only approved venting materials. PVC works for some condensing models, but others need stainless steel.
Maintain the correct slope on horizontal vent runs. Condensing heaters need 1/4 inch slope per foot back toward the heater to drain condensate. Seal all joints with approved high-heat silicone.
7. Mount the Heater and Make Final Connections
Lift the tankless unit onto the wall bracket. Most units weigh 40-60 pounds, so get help if needed. Secure it according to the manual, usually with screws through mounting tabs.
Connect the gas line or electrical supply. Double-check all connections before moving on. For gas, use a soap solution to check for leaks at every joint. Bubbles mean you have a leak that needs fixing.
Hook up the water lines to the heater. Open the shut-off valves slowly and watch for drips. Tighten any connections that leak, but don’t go crazy and crack the fittings.
8. System Startup and Testing
Open a hot water faucet in the house before turning on the unit. This purges air from the lines and prevents air locks. Close the faucet once water flows steadily.
Turn on the gas supply and restore power. Follow the startup sequence in your owner’s manual. Most units have a specific order for pressing buttons or flipping switches.
Set the temperature to 120°F to start. This prevents scalding and saves energy. Run hot water at multiple fixtures to test flow rate and temperature consistency.
Check the vent system during operation. No smoke or fumes should leak from joints. The exhaust should flow freely outside.
Common Installation Mistakes to Avoid
Don’t skip the gas line sizing calculation. A line that’s too small can’t deliver enough fuel. Your heater will shut down or fail to reach set temperature. Check the BTU rating and pipe length chart in the manual.
Wrong venting kills performance and creates safety hazards. Use only approved vent pipe materials. Never mix different types of vent pipe in the same installation. This causes leaks and drafting problems.
Forgetting the expansion tank is a rookie mistake. When water heats, it expands. In a closed system with check valves and backflow preventers, that pressure has nowhere to go. An expansion tank absorbs the pressure and protects your plumbing.
Poor electrical sizing causes breakers to trip constantly. A 40-amp heater needs 40-amp wire and breaker, not 30-amp. Check the manual for exact requirements.
Not flushing the system before startup leaves debris in the heat exchanger. This cuts efficiency and shortens heater life. Run water through the lines before connecting the heater to flush out dirt and pipe shavings.
Ignoring local codes gets you in trouble during inspection. Every area has specific requirements for gas, electric, and plumbing work. Call your building department before you start. Get the required permits and schedule inspections.
When to Hire a Professional
Some tankless hot water installation tasks require licensed professionals. Gas work tops that list in most places. Running new gas lines and making final connections must meet strict safety codes. One mistake can cause fires, explosions, or carbon monoxide poisoning.
Major electrical upgrades need a licensed electrician. If your panel can’t handle the new heater’s power draw, you’ll need service upgrades. This involves working in the main panel, which is dangerous without training.
Complex venting situations call for expert help. If your heater location requires long vent runs with multiple elbows, hire someone who knows the calculations. Improper venting can cause backdrafting and put exhaust gases into your home.
Permit and inspection requirements vary by location. Some areas let homeowners install their own heaters. Others require licensed plumbers for any work on water heaters. Check your local rules before deciding to DIY.
The cost to hire a pro runs $800-$1,500 for labor on top of the heater price. Complex jobs with gas line extensions or electrical upgrades cost more. Get three written estimates before choosing a contractor.
You can read about: How to Install a Heat Pump Water Heater
Find A Local Water Heater Professionals
Looking for expert help with your tankless water heater setup? Professional installation ensures everything meets code and works safely. Licensed contractors have the right tools, and experience, to handle gas lines, electrical work, and venting.
For reliable Tankless Water Heater Installation Eagle Rock services, contact Derks Plumbing. Our certified technicians handle complete installation of tankless water heaters from start to finish. They pull permits, pass inspections, and warranty their work.
Professional installation makes sense for gas tankless hot water install projects. The safety risks and code requirements make DIY risky if you’re not experienced. A licensed plumber knows the local rules and has relationships with building inspectors.
Check contractor credentials before hiring anyone. Verify their license, and references. Ask how many tankless water heater installation projects they’ve completed. Experience matters when dealing with complex systems.
Conclusion
Installing a tankless water heater is a significant home upgrade that provides years of energy savings and unlimited hot water. By following this comprehensive guide on how to install tankless water heater, you now understand the complex steps involved: careful preparation, precise gas and water connections, and absolutely critical venting.
While a DIY approach is possible for very experienced individuals, the technical requirements for gas line upgrades, venting, and electrical hookups make this project one where professional expertise is highly recommended. Make smart, safe choices to enjoy your new endless hot water system.
FAQs
Can I install a tankless water heater myself?
Yes, if you have solid plumbing and electrical skills. Electric models are easier for DIY than gas units. Check local codes first since many areas require licensed professionals for gas work. Improper installation voids warranties and creates safety hazards.
How long does tankless water heater installation take?
Professional installation takes 4-8 hours for straightforward replacements. DIY projects take longer, often spreading across two days. Complex jobs requiring gas line extensions, electrical panel upgrades, or major venting changes can take 2-3 days.
Do I need a permit to install a tankless water heater?
Most areas require permits for water heater replacement. Gas and electrical work especially need permits and inspections. Call your local building department before starting work. Skipping permits can cause problems when you sell your house.
What size tankless water heater do I need?
Calculate based on flow rate and temperature rise. Add up the gallons per minute for all fixtures you’ll run at once. In cold climates, you need higher BTU ratings to heat incoming water. Most homes need units delivering 5-10 gallons per minute.
How much does professional tankless water heater installation cost?
Expect to pay $1,000-$3,500 total including the unit and labor. Gas models cost more to install than electric due to venting requirements. Complex jobs with extensive plumbing or electrical upgrades can run $4,000-$5,000. Get multiple quotes before hiring.
