This is a project that should be taken on only by the serious do-it-
yourselfer.  If not performed correctly, you can cause serious
damage to your home and personal injury to yourself.  I would
always recommend utilizing a professional, whether you call Mr.
Fix-It™, or someone else.  I have received multiple requests to
post a procedure of this type.  Here it is, proceed at your own risk
and with caution.  Make sure you have a helper. - Ben Payne

Normally, the first sign of a heater problem is water dripping from the bottom of the jacket.
This indicates that the tank has corroded through. the cure is the installation of a new
heater, period.  This article covers the replacement of natural gas, and electric water
heaters, the most common kinds.    The following tools are necessary:
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•  Hacksaw or pipe cutter
•  Pipe wrenches
•  Screwdrivers
•  Adjustable open-end wrench
•  Drill and 1/8 inch bit
•  Soldering torch
•  Dolly, or hand truck
The typical overhead-plumbed water
heater hookup is shown in Fig. 1.
Before you can connect the new
heater, though, the old one must be
taken out.
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gas or electricity to the heater.
Drain the heater (Fig. 2). Opening a
hot water faucet will let air into the
system
On a gas heater, separate the vent pipe from the draft hood. It
should lift off after removing the sheet metal screw that holds
it. After making sure the pilot light is out, disconnect the gas
line at the heater and cap it.
Next, remove the heater from its water piping. If connected with
pair of pipe wrenches. Pipes without unions will have to be
unions--removable threaded fittings--take them apart with a
hack sawed off (Fig. 3). Or a pipe/tubing cutter will do the job.
The old heater can now be taken away and disposed of at a
dumpsite.
Take your new heater to its location by
dolly, or hand truck.
Position the new heater so your
piping--particularly a gas vent pipe--will
reach most easily.
Install the heater's new draft hood (gas
heater). Many have legs that insert
into holes on the heater's top (Fig. 4).
Every gas water heater needs proper venting
that's no smaller than the draft hood collar of
the new heater. It's a good idea to use new be
corroded at their present angles. The vent
should go straight up as far as possible. Then
any horizontal run should slope upward at
least 1/4 inch per foot, as shown in Fig. 5.  
Connect the vent pipe with short sheet metal
screws (Fig. 6).
Now you can make the hot and cold water connections. The
easiest way often is using copper flex-connectors, available
from your dealer. Figure 7 shows how flex-connectors fit a
heater's female tapping (left side), or male stub (right side).
At the upper end, the flex connectors make up to a
threaded metal pipe (left) and a sweat-soldered copper
tube (right) using a male adapter. They range in length
from 12 to 24 inches--the 18- and 24-inch lengths being
most practical. Flex-connectors are easily bent to reach
where you wish.
house has threaded metal, sweat-soldered copper, or
thermoplastic piping, and whether it is 3/4 inch or 1/2 inch. No
matter what, though, the old heater should be fitted with a cold
water gate valve (Fig. 8). To keep it from becoming
sediment-fouled, the valve should be placed in a vertical section
of piping.
A vital part of water heater installation
is the provision of a temperature and
pressure relief valve and relief line.
The relief system is designed to let off
excess heat and pressure
automatically (Fig. 10.)
drain valve and open the cold water inlet valve to fill the storage
tank. Opening a hot water faucet will release trapped air in the
top of the tank. Close the faucet soon so water flows readily from
it. Check for leaks.  Check for leaks with a dish detergent
solution used on all gas connections you've either made or
disturbed (Fig. 11). Never test for gas leaks with a flame. If any
leaks are found, turn off the gas right away and fix them.
The wires serving an electric water heater must be the right size, providing the voltage and amperage the heater is
designed for. Unless you know how to work with wiring, a qualified electrician should be hired to wire the heater.
When you turn the heater circuit on, check the electric meter to see whether it is spinning, indicating that the heater
is working.
Water Heater Safety Tips
Water draining from a heater may be quite hot, use care.
While sweat soldering copper tubing, be careful not to start a fire. Wet any wood nearby. Use metal shielding. Make
sure that no gas leaks. Have a fire extinguisher at hand.
The cold water gate valve must be left open all the while a water heater is in use.
Check the relief valve's action periodically to make sure it opens and closes again. Remember that water coming
from the relief pipe may be very hot.
Gas Heater Safety
Use stick pipe dope, or yellow gas line tape, (not white teflon tape), on gas connection threads. Don't use oil-based
compounds.
Check to see that the type of gas you have is suited to the new heater.
Check for the required clearances between the heater and combustible materials (see the heater's owners manual).
Verify that the heater's combustion air needs will be met.
It's a good idea to put a garage-based water heater up on an 18-inch-high (minimum) platform, even though this
calls for making plumbing changes. Some codes require it (for electric heaters, too). Make the platform of 2 x 4's
and 5/8 inch plywood.
Apply stick pipe dope sparingly to the male threads of the heater's flare adapter, keeping the dope back from the
first two threads so it won't get into the gas line. Then it cannot foul the gas controls.
Don't assume a switch or circuit breaker has cut off the electric power. Before you
touch any bare wires, with hands or tools, check the wires with a 240-volt neon test
should glow. Then open the access cover to the heater junction box, removing the
wire nuts or tape from the heater's electrical connections carefully without touching
them. Contact the test prods between the heater's green grounding screw or other
reliable ground and each of the exposed wires in turn (Fig. 12). Furthermore, touch
the prods across the bare wires themselves. If the test light glows at any time, at least
some of the wires are still "live," indicating that power to the heater is not off. Call in
an electrician before proceeding on your heater change. This is critically important,
because electricity, water, and plumbing create a potentially hazardous combination.
serving the heater and remove it.  
Read and carefully follow the manufacturer's lighting instructions.
It may take some time for air to be purged from the gas lines, and a flame should be kept at the pilot orifice until the
pilot lights.
sizzling is okay with a cold storage tank. That's caused by condensed water dripping onto the hot burner. But if a
puddle of water forms under the heater, it's from a leak.
Adjust the temperature control for as low a setting as will provide enough hot water for your largest use (e.g., filling
Do not attach aluminum wires to copper ones inside the heater.
See that the heater is properly grounded, electrically (Fig.13).
Replacing A
Water Heater
Mr. Fix-It™