Water Heater Installation — Cost, Process, Permits & DIY vs Pro

Water heater installation is one of the most common plumbing jobs in a US home — about 8 million units are installed each year. The work is straightforward when it's a tank-to-tank swap with the same fuel; it gets complex when you're switching from tank to tankless, gas to electric, or moving the unit to a different room. This page covers what installation actually involves, what it costs, and how to decide between DIY and hiring a plumber.

How much does water heater installation cost?

Installation cost (labor only, not the unit) typically falls in these ranges in 2026 US pricing:

For total cost (unit + labor), see our water heater replacement cost guide. Installation labor in major metros (NYC, San Francisco, Boston) runs 30-50% higher than the national average; rural areas run 15-25% lower.

Do you need a permit?

In most US jurisdictions: yes. A water heater is a regulated plumbing fixture (water connections + pressure relief), and gas units add fuel-supply regulation. Permit cost is typically $50-200, paid by the homeowner or rolled into the installer's bill. The inspection (usually scheduled by the installer) verifies:

• Code-compliant gas line sizing for the BTU rating
• Proper venting (B-vent for atmospheric, PVC for condensing, Category III for non-condensing tankless)
• Pressure relief valve discharge piped to a safe location
• Expansion tank installed if your home has a backflow preventer or pressure-reducing valve
• Seismic strapping (required in California and parts of the Pacific Northwest)
• Drain pan with overflow drain if the unit is above living space

Skipping the permit creates two problems: (1) some states explicitly void the manufacturer warranty if a permit was required and not pulled, and (2) home insurance can deny claims related to unpermitted work. Always permit.

The actual installation process

Tank-to-tank swap (gas or electric)

1. Shut off water at the cold-inlet valve; shut off gas or breaker
2. Drain the old tank (60-80 minutes for 50 gallons via a garden hose to a floor drain)
3. Disconnect water lines, gas line / electrical, T&P valve discharge, vent
4. Remove old unit (use a hand truck — full tanks weigh 400+ lb; even empty, 130-180 lb)
5. Position new unit; verify level
6. Connect water lines (use flexible braided supply lines for code compliance in most jurisdictions)
7. Install or transfer the pressure relief valve; connect discharge tube
8. Connect gas line (with sediment trap if code) or wire electric circuit (240V dedicated)
9. For gas: connect venting; verify draft
10. Fill the tank fully BEFORE applying power or lighting gas — a dry electric element burns out in seconds
11. Energize and verify operation; check for leaks

Tank-to-tankless conversion

This is the install most likely to be done badly. Additional work beyond a tank swap:

• Upsize gas line — most tankless units need ¾" gas line back to the meter (vs ½" common to tanks). Often the most expensive single line item
• Install dedicated venting — PVC for condensing, stainless Category III for non-condensing. Cannot share an existing B-vent
• Install isolation valves (service kit) on hot and cold for future flushing
• Install condensate trap and drain for condensing models
• Install water softener or scale filter if incoming hardness exceeds 11 gpg
• Wall-mount the tankless unit (vs floor-standing tank)

DIY vs hire a plumber

Reasonable DIY: tank-to-tank swap, same fuel, same location, if you've done plumbing before. The work is mechanical, the connections are standard, and there's no design judgment required. Budget a Saturday and a hand truck.

Hire a plumber:

• Anything involving gas line work (size changes, new runs, or repositioning)
• Tank-to-tankless conversions
• Heat pump / hybrid installs (refrigerant handling, condensate routing)
• Combi boiler installs (hydronic system design)
• Any work requiring a permit if your jurisdiction requires a licensed plumber for the permit
• If you're not certain about the venting code for your unit type and house construction

A plumber's labor charge buys you the permit, the inspection, code compliance, and warranty protection. For a $1,500 unit, paying $500 in labor for proper install protects the $1,500 warranty plus a $300,000 house.

How to choose an installer

• Licensed plumber (verify on the state licensing board)
• Manufacturer-trained for the brand you're installing (Rinnai-trained, Navien Service Specialist, Bradford White-network — see brand-specific dealer pages)
• Quotes itemized: unit, labor, permit, venting, gas line work, condensate, removal of old unit
• Pulls the permit (don't accept "we don't need a permit" — they always do)
• References from 2-3 recent installs in your area

By-brand installation guides

Each major brand has specific install requirements — gas line sizing tables, venting rules, and commissioning steps that differ:

• Rinnai installation guide
• Navien installation guide
• Rheem installation guide
• AO Smith installation guide
• Bradford White installation guide

Related water heater guides

• Water heater replacement — process, signs you need one, planning
• Water heater replacement cost — unit + labor by type
• Tank vs tankless — which to install
• Gas vs electric — fuel decision
• Water heater sizing — what size to install
• Expansion tank — when you need one (most modern installs)

Bottom line

For a tank-to-tank swap, installation is a 3-hour job costing $250-600 in labor — DIY if comfortable, hire if not. For a tank-to-tankless conversion or any work involving gas line changes, the install is the most important decision you'll make — pick a manufacturer-trained installer and pay the permit fee. The "tankless was terrible" complaints you read online are almost always install problems, not unit problems.