Ready to upgrade to endless hot water and lower energy bills? Installing a tankless water heater is a big project, but it’s absolutely possible for a confident DIYer—or a smart investment for professional installation. This guide walks you through how to install a tankless water heater from start to finish, with step-by-step instructions, pro tips, and all the tools and products you’ll need for a safe, reliable job.
Can You Install a Tankless Water Heater Yourself?
- Electric tankless: DIY-friendly for those comfortable with plumbing and basic electrical work. Always follow local codes and manufacturer instructions.
- Gas tankless: Usually best left to licensed plumbers and gasfitters. Gas lines, venting, and code requirements are strict for safety.
- Permits: Always check if your local jurisdiction requires a permit and inspection—this is required in most areas, especially for gas or major electric work.
Planning & Preparation
- Sizing: Choose a tankless unit sized for your household’s peak hot water needs (GPM)—see manufacturer sizing charts.
- Location: Install near the main water line and close to where hot water is used. Allow clearance for service, venting, and code requirements.
- Supplies: Tankless water heater, mounting hardware, shutoff valves, vent kit (gas), appropriate pipe/fittings, T&P valve, pipe insulation, flexible connectors, descaling kit for maintenance.
- Safety: Shut off power, gas, and water before starting any work. Read all instructions and wear proper safety gear.
Step-by-Step: How to Install a Tankless Water Heater
1. Remove the Old Water Heater (if applicable)
- Turn off the circuit breaker (electric) or shut off the gas supply.
- Shut off cold water supply, drain the old tank, disconnect plumbing and electrical/gas lines.
- Remove the old unit and dispose of it according to local regulations.
2. Mount the Tankless Water Heater
- Mark wall studs and use the manufacturer’s mounting template or bracket.
- Secure the unit at the recommended height with adequate clearance around all sides.
- For outdoor models, follow all weatherproofing and clearance guidelines.
3. Connect Water Lines
- Install shutoff valves on both cold and hot water lines for easy future maintenance.
- Use flexible stainless steel connectors for easy installation and servicing.
- Always include a pressure relief valve (T&P valve) if required by code or manufacturer.
- Insulate pipes to reduce heat loss, especially if the unit is in a cold location.
4. (Gas Models) Install Gas Supply and Venting
- Use only approved gas piping and size it for your heater’s BTU input—consult manufacturer specs.
- Check for leaks at every joint using a soapy water solution.
- Install vent kit as specified—most units require stainless steel, concentric, or PVC venting. Slope horizontal vents back toward the heater to drain condensate.
- Terminations and clearances must meet local code (usually at least 12” from windows, doors, or vents).
5. (Electric Models) Wire the Electrical Connection
- Confirm your panel can handle the amperage—many units require a 60–150A dedicated circuit at 240V.
- Use appropriate gauge wire as specified (often #6 or #8 AWG for 240V).
- Connect ground and all wires securely—double-check before restoring power.
6. Fill, Test, and Commission the System
- Open cold water supply, purge air by opening hot taps, and check all connections for leaks.
- Restore power/gas and follow the startup procedure in your manual—set desired temperature (usually 120°F for safety).
- Check for error codes, proper venting, and normal operation. Run hot water at each fixture to confirm function.
Buyer’s Guide: Top Tools & Products for Tankless Installation
- Flexible Water Heater Connectors: Make installation faster and prevent leaks.
- Rinnai Tankless Water Heater Valve Kit: For easy annual maintenance and flushing.
- Pipe Insulation: Reduces heat loss and protects pipes in cold areas.
- Channel-Lock Pliers & Pipe Wrench: Must-haves for all plumbing work.
- Combustible Gas Leak Detector: For gas installs—essential safety!
- Descale/Flush Kit: Required for yearly tankless maintenance.
Top Product Reviews: Installation Essentials
Rinnai V94iN Natural Gas Tankless Water Heater
- 9.8 GPM, Energy Star rated, 10-year warranty
- Top choice for whole-house gas installation
- Clear install instructions and strong support
Final Verdict: Most popular, reliable gas tankless for new installs.
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EcoSmart ECO 27 Electric Tankless Water Heater
- 27 kW at 240V, 6.5 GPM, lifetime warranty for residential use
- Best DIY-friendly electric tankless model
- Compact design, fits in tight spaces
Final Verdict: Ideal for small homes, condos, or electric upgrades.
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SharkBite Flexible Water Heater Connectors
- No-sweat, push-to-connect brass fittings—save time and prevent leaks
- Perfect for tankless and traditional water heaters
- Fits 3/4” copper, PEX, or CPVC pipe
Final Verdict: Best upgrade for any tankless or tank install.
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Comparison Table: Tankless Water Heater Installation Essentials
| Product | Type | Main Use | DIY Friendly | Price Link |
|---|---|---|---|---|
| Rinnai V94iN | Gas Tankless | Whole house | No (pro recommended) | View |
| EcoSmart ECO 27 | Electric Tankless | Whole house | Yes (skilled DIY) | View |
| SharkBite Connector | Plumbing Fitting | Connect water lines | Yes | View |
FAQ: Installing Tankless Water Heaters
- Can I replace a tank with tankless in the same spot?
Usually, but plan for new venting (gas), different water line connections, and possibly electrical upgrades. - How long does installation take?
Professional installs typically take 4–8 hours. Skilled DIYers may need a full day, especially for new wiring or venting. - Do I need to upgrade my electrical panel?
Electric tankless units often require a 200A panel and dedicated breakers. Check specs before buying. - What’s the hardest part for DIYers?
Gas lines, venting, and main panel wiring are the toughest—always hire a pro if unsure. - How do I maintain a tankless heater?
Flush annually with a descaling kit to keep it efficient and problem-free.
Conclusion
Installing a tankless water heater can be a major upgrade for comfort, energy savings, and convenience. Whether you go DIY for an electric model or hire a pro for a gas system, follow this guide for safe, reliable results. Always size and locate your unit carefully, use top-quality materials, and never cut corners with code or safety. Ready to enjoy endless hot water? Grab your tools, use the buyer’s tips above, and transform your home’s hot water forever!