Gas Water Heater Installation

here's how to replace a gas water heater

first check the labels on your current

tank it will note size and energy

specifications which are helpful when

buying a new heater also make sure your

venting works with this test close all

your windows and doors turn on all the

gas appliances and exhaust fans turn up

the tank temperature for a few minutes

then hold an extinguished match near the

vent hood the smoke should pull into the

hood if it blows back you have a venting

problem call a pro for help

next check your home's water pressure

with a pressure gauge on your outdoor

spigot fifty to sixty psi is ideal if

psi is higher than eighty you can lower

it with a pressure reducing valve

installed after the main water shut-off

an inline pressure gage and a thermal

expansion tank are good to have to the

expansion tank helps alleviate excess

pressure in the lines you can install an

expansion tank easily with push-fit

fittings they simply slide onto the pipe

no soldering needed and to remove use

the simple removal tool if you decide to

solder deburr and clean the pipes and

fittings apply soldering paste and

assemble then heat the fitting and


the expansion tank pressure must be the

same as the main water pressure use a

hand air pump to increase the pressure

or depress the valve to lower it to

remove the old heater turn off the gas

and use a wrench to disconnect the gas

pipe from the control valve then detach

the venting open a faucet on hot and let

it run until the water is cool now shut

off the cold water supply and connect a

garden hose to the drain valve open the

valve and empty the tank into buckets or

a drain opening a hot water faucet can

help the tank drain faster when the tank

is empty remove the discharge pipe from

the temperature and pressure relief

valve also called the T&P relief valve

disconnect the water supply pipes if you

have to cut them leave them as long as

possible then remove the old tank to

install the new tank set it in a drain

pan avoid possible flooding by routing

to a drain install the discharge pipe on

the T&P relief valve this valve opens

when temperature and pressure are too

high if you don't have a floor drain

place a bucket under the discharge pipe

it should be no more than 6 inches above

the bucket hooking up the water is easy

with a flexible hose kit and it's

recommended for earthquake safety make

sure your kit also has a gas hose apply

plumber's tape on the threads of the

heat trap nipples and attach the hoses

some areas require dielectric fittings

to reduce corrosion between two

different metals add plumber's tape to

the connector body threads secure it to

the hose then hold the hose up to the

pipe it should have a little slack mark

and cut the pipe remove the burrs

and slide the compression nut onto the

pipe push the pipe into the fitting and

tighten the nut

if required by code install seismic

straps to help prevent earthquake damage

they brace the water tank against the

wall to avoid toppling over next remove

the aerator from the nearest faucet and

open the hot side turn on the cold water

supply and check your connections for

leaks if everything is good

continue filling the tank when water

runs from the faucet the tank is full

let it run for about three minutes

to empty air out of the tank now secure

the venting to the new exhaust hood to

connect the gas line first make sure the

tanks control knob is off wrap the

threads of the fittings with gas

plumber's tape insert a flare nut into

the control valve and screw the other

flare nut into the gas line then connect

the hose turn the gas supply on and use

leak detection solution to check for

leaks it will bubble if you have a leak

tighten the connections if needed to

light the unit turn the control knob to

pilot and press then push the igniter

button the light will blink when it's

lit 120 degrees Fahrenheit is the

recommended temperature setting perform

the vent test again and call a pro if

there's a problem it's a good idea to

have a carbon monoxide detector near the

heater finish by installing the air

filter after a few hours check the

discharge pipe a dripping pipe usually

means the pressure is too high

turn it down below 80 psi also if a

faucet stops working after installation

take out the aerator and clean it and

then run hot water to remove loose

sediment installing a new water heater

will give you hot water for many years

want more great ideas and how-tos

go to or click to

subscribe next learn how to install a

vessel sink