How to Switch from Tank to Tankless Water Heater
On this page 6 sections
To switch from a tank water heater to a tankless water heater, first turn off the power and water supply, then disconnect the tank heater, install the tankless unit according to the manufacturer’s instructions, ensuring proper venting and plumbing connections, and finally, restore the power and water supply to test the system.
Upgrading to a tankless water heater can save energy, space, and money over time. This guide covers everything from sizing to installation for a successful conversion.
When to Make the Switch
Consider switching when:
- Your current tank is 8+ years old
- You need more hot water capacity
- Energy bills are rising
- Space is limited
Tankless units last 20+ years compared to 10-15 for tanks. Newer models achieve up to 94% energy efficiency versus 70% for standard tanks.
Choosing the Right Tankless Water Heater
Gas vs Electric
Gas models provide higher flow rates but require proper venting. Electric units are easier to install but may need upgraded wiring. Compare gas and electric water heaters to find your best option.
Sizing Your Unit
Calculate your peak demand:
| Fixture | Flow Rate (GPM) |
|---|---|
| Shower | 2.0-2.5 |
| Dishwasher | 1.0-2.0 |
| Washing Machine | 1.5-2.5 |
Add up simultaneous uses to determine required capacity. For whole-house systems, consider a unit with recirculation pump.
Installation Process
1. Remove Old Water Heater
- Turn off water supply and power/gas
- Drain the tank completely
- Disconnect all plumbing and electrical
- Remove the unit (may require help)
2. Prepare for New Installation
Gas models often need:
- Larger gas line (typically 1″ diameter)
- Proper venting (stainless steel recommended)
- Combustion air supply
Electric models may require:
- Dedicated 240V circuit
- Upgraded electrical panel
- Proper wire gauge
3. Mount and Connect New Unit
Follow manufacturer instructions for:
- Wall mounting (use sturdy brackets)
- Water line connections (use dielectric unions)
- Gas/electrical connections
- Vent installation (for gas models)
According to Department of Energy, professional installation is recommended for most tankless conversions.
Water Heater Owner's ToolkitFix the common faults yourself, keep it running for years, and know when a repair is money wasted.No-hot-water flowcharts, gas and electricFlush, anode, relief valve and descaling stepsRepair-or-replace calculator (Excel)Post-Installation Considerations
Maintenance
Annual flushing prevents mineral buildup. Use a quality descaling solution for best results.
Temperature Settings
Set between 120-140°F. Higher settings reduce efficiency and increase scaling. Learn ideal temperature settings for your needs.
Water Pressure
Tankless units require minimum flow rates to activate. Consider low-flow fixtures if you experience intermittent operation.
Cost Considerations
Typical costs include:
- Unit: $600-$3,000
- Installation: $1,000-$3,000
- Upgrades (gas/electrical): $500-$2,000
According to Consumer Reports, tankless heaters can save $100+ annually on energy bills.
Common Challenges
Be prepared for:
- Cold water sandwich effect (brief cold between hot)
- Higher upfront costs
- Possible need for water softener in hard water areas
- Longer wait for hot water at distant fixtures
Related pick: Check price on Amazon
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