If you have some basic plumbing
experience, you can replace a
water heater yourself and save
$200 to $400 in plumber's fees.
We'll show you how to replace a conventional
natural gas water heater. The
procedure is the same for a propane
heater. If you choose a “power vented” gas
model, all the water and gas connections
are the same as we show, but the venting
steps are different. For more, search for
“power-vented water heater” above. Replacing an
electric water heater is a little easier. All
the water connections are the same and
you don't have to deal with gas piping or
venting. For details on situations different
from the one we show here (such as electric
models, plastic water lines or copper
gas lines) search for “replace water heater” above.
Time, materials and money
If you have lots of plumbing experience,
you might be able to complete this project
in half a day. But we recommend you start
in the morning so you have plenty of time
to get the job done and not leave your
family without hot water overnight. You'll
need a helper to carry the old unit out and
the new one in. Check with your trash
hauler or recycling center to find out how
to dispose of the old heater.
A new water heater will cost from $250
to $500, depending on the size, efficiency
and warranty. The materials you'll need
for the installation depend on your situation
and local codes.
Even if you've worked with plumbing
and gas lines in the past, play it safe and
contact your local department of inspections.
Get a permit (if required), and go
over your installation plans with an
Turn off the gas and water
1 of 3
Photo 1: Shut off the gas
Shut off the gas by
turning the handle a
quarter turn. In the “off”
position, the handle is perpendicular
to the pipe.
2 of 3
Photo 2: First disconnect the gas
Disconnect the gas at
the “union” fitting.
Place the larger wrench
on the nut and hold the
union's collar with another
wrench. Start with the
wrenches a quarter turn
3 of 3
Photo 3: Cut the cold water line
Cut the cold water line
above the old gate
valve to make room for a
new ball valve. Cut the
hot water line at the same
To get started, turn off the gas at the valve
near the water heater (Photo 1).
If the “isolation” valve above your water
heater is a gate valve (Photo 3), we recommend
that you replace it with a ball
valve (Photo 4). Be sure to choose a “fullport
valve.” Gate valves often leak or won't
close tightly. To replace the valve, you'll
have to shut off the water at the main
valve (usually near the meter). That
means your whole house will be without
water until you install the new valve. If
you already have a ball valve or if you
choose to leave the old gate valve in place,
you can simply shut it off. That way the
rest of the house will have cold water
while you work (toilets will still work!).
With the water and gas off, drain the
water heater. Attach a garden hose to the
drain valve at the bottom of the tank,
route it to a floor drain and open the
drain valve. To allow air into the hot water
lines and speed up the draining process,
go to the highest faucet in the house and
turn on the hot side only (on single-handle
faucets, push the lever all the way to
If your valve doesn’t look
like this one, see “Old gas valves
Disconnect the gas, vent and water lines
Disconnect the gas line at the union
(Photo 2). Then disassemble the threaded
“tee” and “drip leg” and remove the nipple
from the water heater gas control valve.
Don't throw them away—you'll need
them for the new water heater. If your gas
line is copper or a flexible supply line, just
unscrew the nut.
To disassemble the vent piping, remove
the sheet metal screws. Wear gloves; the
ends of the metal piping are sharp. You
can reuse the vent pipes if they're in good
shape. But if you find even slight holes,
cracks or corrosion, toss them into the
trash. New pipe is inexpensive and leaks
can allow deadly carbon monoxide to
build up in your home.
Next, cut the copper water lines with a
tubing cutter (Photo 3). If you have copper
corrugated water lines, simply disconnect
the nuts at the water heater. If you
have galvanized steel pipes, disconnect
unions just as we did with the gas union
shown in Photo 2. Also unscrew the blow
tube from the temperature and pressure
(T&P) valve. You may be able to reuse it
on the new water heater.
At this point, the old heater should have
drained enough so it can be moved off to
the side (with a helper). If the heater isn't
draining fast enough, sediment may be
clogging the valve. Allow it to drain as
long as possible and then move the heater
outside so you can remove the drain valve
from the tank.
Reconnect the water
1 of 2
Photo 4: Install new valves
Reconnect the water.
Install new valves first
so you can turn on the
water to the rest of the
house. Then install nipples,
followed by threaded
fittings and “stubs” of
pipe. Hold the final section
in place to mark the
2 of 2
Photo 5: Make the final connection
Make the final
“slip” couplers. Be sure
the coupler doesn't slide
down as you heat it.
Set the drain pan into place with the
opening facing the floor drain. Get someone
to help you lift and set the heater in
the pan. If you're replacing the isolation
valve, solder on the new ball valve next.
Screw dielectric nipples into the new
water heater. These plastic-lined nipples
reduce corrosion and increase water
heater life. Some water heaters come with
dielectric nipples already installed (buy a
set if yours doesn't have them). Be sure to
coat the threads with pipe thread sealant
or wrap with Teflon tape. Next, solder
female threaded copper pipe fittings to
short lengths of copper tubing and set
them aside to cool. Tighten the cooled fittings
onto the nipples. Then add short
sections of pipe below the valves (Photo
4) and make the final connections with
“slip” couplers (Photo 5). You must use
slip couplers—standard “stopped” couplers
won't work. For tips on soldering
copper pipe, search for “solder” above.
Thread a “blow tube” onto the T&P
valve. If the old blow tube is too short, you
can use 3/4-in. galvanized steel pipe or
copper pipe (along with a male threaded
fitting). If you use galvanized pipe, cut off
the threads on the bottom to prevent
someone from capping off the blow tube
if the T&P valve leaks.
Install the new vent
1 of 1
Photo 6: Connect the vent pipe and hood
Connect the vent pipe
to the hood with sheet
metal screws. Never use a
reducer, even if the hood's
opening is smaller than
the vent pipe.
Snap the new draft hood onto the water
heater and secure it with sheet metal
screws. Check the installation manual for
the recommended diameter vent pipe for
your new heater. If the recommended vent
pipe diameter is larger than the vent hood
opening, don't install a reducer. Measure a
straight section of new galvanized vent
pipe to rise as high as possible before you
install the adjustable elbow (the higher
the rise, the better the draft). On any horizontal
sections of vent, make sure the
pipe slopes down toward the water heater
1/4 in. per foot of pipe. Bend out small
sections of the pipe and attach it directly
to the vent hood with screws (Photo 6).
Then continue installing new vent pipe
sections and connect to the flue. Most
plumbing codes require a minimum of
three screws for each vent pipe joint. For
tips on cutting metal venting, search “sheet metal” above.
Hook up the gas
1 of 3
Photo 7: Reconnect the gas
Reconnect the gas.
Hold back the control
valve to avoid damaging
it. Then screw the drip leg
into the tee.
2 of 3
Photo 8: Determine correct nipple length
Measure between the
union and the tee and
add 1 in. to determine the
correct nipple length.
3 of 3
Photo 9: Test for leaks
Test for leaks by
water onto every connection.
If you see bubbles,
tighten or reconnect
Apply gas-rated pipe thread sealant or
tape (don't use standard white Teflon
tape) to the gas nipple and thread it into
the new gas control valve. Tighten the nipple
using two pipe wrenches (Photo 7).
Assemble the tee and drip leg using the
same two-wrench technique.
If the old section of pipe below the
union no longer fits, you'll need to measure
for a new nipple (Photo 8). Make sure
you assemble and tighten the gas union
before you measure the length for the
intermediate nipple. Add 3/4 in. to 1 in. to
this measurement and buy a new nipple.
When the gas connections are complete,
turn on the gas and check for leaks (Photo
9). You can buy leak detector in a convenient
spray bottle ($3) or mix your own
solution (one part dish detergent, two
Open the water valves and an upstairs
faucet and fill the tank. Leave the faucet
open until water flows out. Then shut it
off and check the new water connections
for leaks. Open the gas valve and light the
pilot light following the manufacturer's
instructions. You're in for a pleasant surprise
with your new water heater—manufacturers
have done away with the old
“match-lit” pilot system. Instead of igniting
the pilot with a match or lighter, you
just push a button.
When the burner fires up, test for
“backdrafting,” which can allow deadly
carbon monoxide into your home. Close
all doors and windows and turn on
kitchen and bath exhaust fans. When the
burner has been running for at least one
minute, move an incense stick around the
draft hood. The smoke should be drawn
up into the vent. If not, the exhaust may
be entering your home. Turn off the gas
and call in a professional plumber.
Finally, set the thermostat to a safe temperature.
(For help, search for “water heater
temperature” above.) In about two hours, you'll
have enough hot water for a well-deserved
Replace old grease-pack valves with new
generation ball valves.
Old Gas Valves Can Leak
The “grease-pack” valves found
in older homes tend to leak as
they age. Even if your local code
doesn't require replacement, we
recommend you install a ball-type
gas valve instead ($10).
Replacement isn't difficult; you
just unscrew the old valve and
screw on the new one. But you
will have to turn off the main
gas valve and later relight pilot
lights. If you don't know how to
handle these tasks, call in a professional
plumber and expect to
pay $80 to $150.
Here are some common
code upgrades you
may find on your new
Local Code Requirements
You'll find lots of accessories for your new water
heater at the home center. Some are required by
local codes; others are just good ideas. Plumbing
codes vary, so check with your local inspector.
1. Gas shutoff valve
All codes require a gas valve near the water
heater. If you have a “grease-pack” valve, see "Old Gas Valves Can Leak" section above.
2. Earthquake straps
These straps prevent a water heater from tipping
over and are required in earthquake-prone
areas. $12 per pair.
3. Flexible gas line
A flexible gas line can withstand movement and
is usually required in earthquake-prone areas.
They're easier to connect than steel pipe, but
they're not allowed everywhere, so check with
your inspector. $15.
4. Drip leg
Any dust or grit in the gas line falls into this
short section of pipe before it can reach the
water heater's control valve. The required
length of the drip leg varies.
5. Isolation valve
All codes require a valve on the cold water line.
Though not required by codes, a second valve
on the hot line makes future water heater
replacement easier. $10 each.
6. Flexible water lines
These flexible lines withstand movement and
are required in earthquake zones. But you may
want to use them just because they're easy to
install. $20 per pair.
7. Overflow pan
Most plumbing codes require a pan and drain
pipe in locations where a leak can cause damage.
But installing a drain pan is a good idea for
any location. $18.
8. Expansion tank
Some codes require an expansion tank to
absorb the pressure created when heated water
9. Blow tube
The T&P valve releases pressure, and a “blow
tube” directs the scalding hot water toward the
floor. The required distance between the blow
tube and floor is usually 18 in. or less.
Attach bonding clamps to the hot and cold lines going
to your water heater. Then
connect a cable
to the clamps.
Water Heater Bonding
New Jersey building codes require a
bonding wire be installed between the cold/hot
pipes and the gas line. The majority of
local codes don't require the bonding
wires but they do serve a purpose.
According to the experts we spoke with, bonding
wires may actually extend the life of
the water heater by diverting electrolysis
from the anode rod and tank—even
on electric models. So whether or not
your local code calls for the bonding
wire, you may want to install one to get
more life out of your water heater. This
little project is brain-dead simple. It only
costs about $10 and takes about 10