Water heater guide

Can you replace a water heater yourself?

Plenty of handy homeowners can swap a water heater. Whether you should depends on the fuel, the venting, and what your town requires. Here's what to know before you start.

Updated October 21, 2026 · 6 min read · By the Heater Doctor team

Plumber wheeling a new tank water heater through a home hallway on a hand truck

Short answer

Sometimes, but check your local rules first. A. O. Smith notes that many municipalities require a permit and an inspection to replace a water heater. Some places are stricter: Massachusetts requires a permit before any plumbing or gas fitting work is replaced. Gas heaters involve gas lines and venting, and most homeowners hire a licensed installer for them.

Permits: the first question

A. O. Smith's installation guide says municipal rules vary, but many require permits and inspections, and your local building department can tell you what applies. Two examples:

Massachusetts: 248 CMR 3.05 says plumbing or gas fitting work can't be installed, altered, removed, replaced or repaired until a permit is issued (see our Massachusetts page).
Los Angeles: the city's building department says a plumbing permit is required to replace a gas water heater in a single-family home, unless the work is done by a contractor registered with the department as a Certified Licensed Contractor.

Permits exist because a badly installed water heater can leak gas, vent carbon monoxide into the house or build dangerous pressure. The inspection is a second set of eyes.

What the job involves

Draining and removing the old tank. A 40 or 50 gallon tank is heavy and awkward, even empty.
Water connections, including the relief valve's discharge pipe.
Thermal expansion control if your system is closed (see expansion tanks).
Gas and venting on gas models. A. O. Smith says improper gas connections can create serious safety risks.
Electrical on electric models. A. O. Smith's manuals say the heater must be grounded per the National Electrical Code and local codes.
Filling before firing. A. O. Smith warns that turning a heater on without a full tank can seriously damage it. On a new electric heater, it says that's almost always the cause of a burned-out upper element.

When DIY can make sense

A like-for-like electric swap, same size and location, where your town allows homeowner permits and you're comfortable with plumbing and 240-volt wiring. Even then, pull the permit and get the inspection.