⚡ SheetCraft is experimental — send feedback or vote on guides to help us improve.
← Back to Home

Tankless Water Heater Installation Guide

advancedHome Repairhalf day

This comprehensive guide provides step-by-step instructions for installing a tankless water heater, making it an ideal resource for homeowners and DIY enthusiasts. You will learn how to navigate local permits, prepare your existing plumbing, and securely mount and connect your new unit.

Safety Warnings

  • Gas-fired installations require professional venting to avoid fire hazards and carbon monoxide buildup.
  • Electrical installations require direct wiring into the home's service panel; ensure power is off at the circuit breaker.
  • Always check for gas leaks (rotten egg odor) before igniting any gas-powered unit.
  • Scalding risk: Do not set water temperature above 120°F.

Tools Needed

Phillips #2 — Cross-head driver for tightening and loosening screws
Buy →
Adjustable 8-inch — Wrench for gripping and turning nuts and fittings
Buy →
Tubing cutter — standard
Buy →
Soldering iron — standard
Buy →

Materials

Copper tubing — 6-inch lengths(as needed)
Buy →
Teflon tape — standard(1 roll)
Buy →
Temperature and pressure relief valve — matched to heater rating(1)
Buy →
Copper couplings — standard(as needed)
Buy →

As an Amazon Associate we earn from qualifying purchases.

Steps

1
Consult the manufacturer's installation manual and contact your city or town to obtain necessary permits and verify local building codes.
2
If replacing an old unit, turn off the cold water supply valve, shut off the gas valve or circuit breaker, and drain all water from the existing system.
3
Mount the tankless water heater to the wall, ensuring it is secure and aligned with existing water and gas/electric lines.
4
Install the temperature and pressure relief (TPR) valve into the designated opening, applying Teflon tape to the threads to prevent leaks.
5
Solder copper adapters and pipes to connect the unit to the home's water lines, using elbow joints if the pipes do not align perfectly.
6
Connect the fuel source by either wiring the unit into the electrical service panel (following US color codes) or connecting the gas line using a pipe joint compound.
7
Turn on the cold water supply and open a hot water faucet to purge air from the system and check all joints for leaks before powering on the unit.
8
Activate the unit by flipping the circuit breaker or turning on the gas supply, then use the digital controller to set the temperature to 120°F.
9
Since this installation involves gas and high-voltage electricity, have a licensed plumber or electrician perform a final inspection to ensure the system is up to code.

Pro Tips

  • To maximize efficiency, consider installing a water filter before the heater to reduce mineral buildup.
  • If the household has high simultaneous hot water demand, consider installing two or more tankless units.

When to Call a Professional

Gas and electrical connections for tankless water heaters must be handled by a licensed plumber or HVAC contractor.

Share this guide