Replacing a Water Heater

Installing a gas water heater

If the new water heater is the same size as the old one and has connections in the same places, hooking up the water, gas, and flue will be simple. If you need to move any lines, the job will take longer.

The system should include a shutoff valve for the cold water line to the water heater (but not for the hot-water line) and the gas line. If not, install them when you install the new water heater.

In an area that experiences earthquakes, local codes may require that you chain or strap the water heater firmly to a wall.

Arrange for disposal of the old water heater. Your local waste hauler may have special requirements.


About a day for most installations

Groove-joint pliers, screwdriver, pipe wrenches, adjustable wrench, tools for cutting and joining pipe, two-wheel cart, torpedo level, hammer

Assembling supply pipe and gas pipe, maneuvering and leveling a large appliance, working with a flue

Clear a path for removing the old unit; prepare the household to be without hot water for a day; check local codes.

New water heater, shims, gas pipe or flexible connector, water pipe and/or flexible connector, heat trap nipples, pipe-thread tape, flue extension (optional), pressure-relief valve

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Step 1

Turn off the gas shutoff valve (so the handle is perpendicular to the pipe). Shut off water and allow the tank to cool. Drain the tank. If there is a gas pipe union, use two pipe wrenches to disconnect it. If there is a flexible connector, disconnect it.

Step 2

Disconnect the water lines. If there is no flexible connector or union to disconnect, you may have to cut through a solid copper pipe. Use a tubing cutter to make a clean cut so you can connect the new line to it.

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Step 3

Once the flue has cooled, detach it from the water heater. Tie the flue up to keep it out of the way. With a two-wheel cart, remove the old unit. Mineral deposits make it heavier than a new unit.

Step 4

Carry or wheel in the new water heater. Position it so the water, gas, and flue connections are as easy to reach as possible. Use a level to check the unit for plumb and shim the legs if necessary.

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Step 5

Install heat-trap nipples to the water heater inlets. Install the blue nipple, its arrow pointing down, to the cold water inlet. Install the red nipple, its arrow pointing up, to the hot-water inlet. Tighten both with a pipe wrench. Run PVC from the pressure-relief valve to a floor drain.

Flexible Water Connectors

If flexible water lines attach to the old water heater, simply unscrew the nuts with an adjustable wrench to disconnect. Check that the old fittings will work with the new; you may need to buy new lines or a male or female adapter. Check local codes.

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Step 6

Before hooking up the supply lines, you may need to install an adapter. For a copper pipe that has been cut, sweat a male adapter to each pipe.

Step 7

Connect the water supply tubes to the heat-trap nipples. Buy connectors approved by local codes, checking that they fit at both ends. If necessary use reducer fittings to make the transition.

Step 8

Connect the gas line. A hard-piped gas line should have a drip leg to collect condensation and dirt that can hinder the burner's efficiency. Wrap the pipe threads with yellow pipe-thread tape (made for gas lines). Tighten connections securely using two pipe wrenches.

Step 9

Do not light the pilot until you are sure there are no leaks. Turn on the gas. Test for leaks by spraying with gas-joint testing fluid (shown) or by pouring a strong soap-and-water mixture on each joint. Bubbles indicate a leak. Tighten leaky fittings. Recheck if necessary.

Step 10

Follow the manufacturer's instructions for lighting the pilot. Usually this involves lighting the pilot while holding down the reset button and continuing to hold it for a full minute before releasing and turning on the burner.

Attaching a Flue: Step 1

If the new heater is the same height as the old water heater, you can simply hook up the flue in the same way. If you need to add piping, measure and cut pieces to fit with a pair of tin snips.

Attaching a Flue: Step 2

Connect the pieces by driving three or four sheet metal screws into each joint. Test to make sure the flue draws and install a carbon monoxide detector in the room. If you have any doubts about the flue, have the gas company or a plumbing and heating contractor inspect it.

Comments (9)
rbacon7323 wrote:

Is it normal for water heater to have a small amount (about 1/4") of water in the bottom of the cylindrical case?

9/10/2017 03:11:44 PM Report Abuse
commercialbuild wrote:

transition fitting

7/20/2017 06:02:51 PM Report Abuse
Kim36330 wrote:

plumbing codes

10/26/2015 05:05:55 PM Report Abuse
Kim36330 wrote:

code requirements

10/26/2015 05:04:57 PM Report Abuse
Kim36330 wrote:


10/26/2015 05:03:09 PM Report Abuse
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