Replacing a Water Heater

Out with the old, in with the new

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Photo 1: Shut off the gas and water

Turn off the gas to the water heater by turning the nearby shutoff valve a quarter turn. When off, the handle should be at a right angle to the pipe. Shut off the main water supply as well and drain the lines by opening a faucet on the lowest floor.

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Photo 2: Drain the water in the tank

Attach a garden hose to the drain valve and drain the water left in the tank. Caution: The water will be scalding hot! Disconnect the gas line at the nearby union with a pair of wrenches and unscrew the pipe from the gas control valve with a pipe wrench.

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Photo 3: Cut off the water lines

Unscrew the vent pipe from the vent hood and move it to the side. Then cut the hot and cold water lines with a tube cutter. (Unscrew unions for galvanized pipe or the nuts on flexible connectors if you have them.) Slide the old water heater out of the way.

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Photo 4: Attach the relief valve

Wrap the threads of the new temperature and pressure relief valve with Teflon tape (three turns). Screw it tightly into the tank with a pipe wrench. Attach a copper discharge pipe (see Fig. A for routing details).

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Photo 5: Attach pipe assemblies

Solder new copper adapters to 6-in. lengths of 3/4-in. copper and screw the assemblies into the hot water outlet and cold water inlet ports in the top of the tank. Add short, plastic lined nipples to shield against galvanic corrosion, especially if you have hard water or if they're required by local codes.

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Photo 6: Attach the water lines

Slide the new water heater into place, recut or extend the old tubing to meet the new, and solder the tubing together using copper slip couplings. If the tubing doesn't line up, offset the lines as needed with pairs of 45-degree elbows.

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Photo 7: Reattach the vent

Reconnect the vent. Shove it tightly over the draft hood and anchor it with three 3/8-in. No. 6 sheet metal screws. Predrill the holes. The vent should rise at least 12 in. vertically before turning at the first elbow.

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Photo 8: Use two wrenches to attach the gas line

Reconnect the gas line. Coat the threaded ends with pipe joint compound and screw the first nipple into the gas valve. Use two pipe wrenches to avoid stressing the valve. Reassemble the remaining nipples, finishing up with the union (Photo 2). Then follow these four steps to fill the tank: (1) Close the drain valve; (2) turn the water back on at the main shutoff and open the cold water valve to the water heater (leave it open); (3) turn on a nearby hot water faucet until water comes out; and (4) inspect all the joints and fittings for water leaks.

We're replacing a natural gas water heater in our demonstration. The steps for replacing a propane water heater are exactly the same, and those for an electric water heater are similar.

In any case, play it safe. Call your local department of inspections and ask if you need a permit. And make sure a plumbing or electrical inspector checks your work.

Your water heater is dead when the tank leaks. The telltale sign that your water heater needs replacing is a slow drip underneath, usually showing up as a trail of rusty water. This means that the steel tank has rusted through and can't be fixed. Other symptoms, such as insufficient or no hot water, usually signal other problems that you can fix.

If you spot a drip, plan to replace the water heater right away. Don't wait until the leak gets bad. Most residential water heaters cost $150 to $400 for either gas or electric, plus $200 to $450 if you have a plumber install it. More expensive gas water heaters with special venting systems also are available. But they're more difficult to install, and we won't deal with them here.

New water heaters come with installation instructions and lots of warnings to make sure you handle the gas, electrical and other connections safely. In this article, we'll supplement those basics with techniques and “real world” advice from several professional plumbers.

But take heed: You'll be working with natural gas, propane or electricity, all of which are hazardous. If you don't feel confident, call in a pro to take care of the tough parts. And have your work inspected when it's done.

Plumbing codes vary by region. Describe your planned installation to your local plumbing inspector, including the types of materials you intend to use for your new connections. Better to get guidance first so you don't have to change things later!

• Measure the height of your old water heater and buy a new one the same height so you don't have to change the length of the water, gas or electrical lines.
• The drain valve (Photo 2) on old water heaters often clogs up. If the water drains slowly, be patient. CAUTION: It's scalding hot!
  TIP: Turn your water heater off two hours in advance to allow the water to cool.
• Water heaters weigh about 150 lbs. You'll need a strong helper or a dolly when you move the old one out and wheel the new one in. Garbage services typically charge about $25 to take the old one.
• Before you start, buy the tools and materials shown here at a plumbing supply or hardware store or a home center. Check the sizes of the water supply pipes (most will be 3/4 in. like the ones in our photos) and buy the right-size fittings. With everything on hand, you'll need four to six hours to complete the job (assuming no big hitches!).
• The temperature and pressure relief valve is a safety device that limits tank pressure and keeps it from exploding (Photo 4). A new one must be included with every installation. For the valve to work properly, the discharge pipe must be kept free of obstructions (Fig. A).
• In regions with highly mineralized water, or where required by local codes, use 3/4-in. plastic-lined nipples (about $2 each; Photo 5 and Fig. A) for joining different metals, usually copper tubing to the steel tank. This slows corrosion.
• When connecting the water lines, solder the copper fittings before you screw them to the tank so you don't heat the tank itself while soldering (Photo 5).
• Use “slip” couplings to connect the old and new lines (Photo 6). Unlike regular couplings, they don't have an internal stop. You can slide them on, align the copper tubing, then slide them back and center them over the joint.
• The new inlets and outlets on the tank don't always line up with the old supply lines. Solder in a pair of 45-degree fittings to offset each line if necessary. Also replace the old shutoff valve with a new ball valve while you're at it (Photo 6). Vent diameters are sized according to the heat output of the water heater. You might have to increase or decrease the vent size to ensure the best draft.
  CAUTION: If you're unsure if your chimney has a liner, ask your plumbing inspector.
• Make gas connections with solid steel pipe (Photo 8) or soft copper with flare fittings (Fig. A). Both are more reliable and less expensive than flexible stainless steel connectors, which are not always permitted. Use rigid copper rather than flexible copper water supply lines for the same reasons.
• If you locate your water heater where leakage could cause damage to the floor or other parts of the house, set a pan of an approved size under it (metal for gas water heaters). The pan must have a drain tube that leads to a house drain or other approved location (outdoors where permitted). The temperature and pressure relief valve discharge tube also must lead to a drain if leakage would damage the floors. If routing is difficult, discuss options with your local plumbing inspector.
• If you live in an earthquake-prone region, strap the water heater to the wall with special straps (Fig. A; available at plumbing stores and home centers). Your plumbing inspector will tell you if they're required.
• Set the new water temperature setting to no more than 120 degrees F. to avoid scalding.

Gas water heater details

Figure A: Gas Water Heater Details

To print out this image, see the Additional Info at the end of this article.

Connections for steel and plastic pipe

Figure B: Connections for Steel and Plastic Pipe

Many homes have galvanized steel or plastic (CPVC) water supply pipes. Galvanized steel pipes are difficult to replace. We recommend that you remove the pipes back to the nearest tee, screw on a plastic-lined galvanized nipple and complete the connections with copper as shown in our photo series.

Because of potential heat buildup, keep plastic pipe at least 6 in. away from the vent and tank. Make a transition from plastic to copper with a special coupling that's available wherever CPVC is sold.

Flexible copper connectors are easier to install than solid copper, especially when the existing pipes and the tank inlets don't line up. But not all local codes allow them. If yours does, take special care not to pinch or kink them. You could get a leak.

Check for backdrafting

Most water heaters rely on a natural draft to draw combustion fumes up the flue. If the draft doesn't work, those fumes, possibly containing deadly carbon monoxide, will spill out into your home. After completing your installation, check the draft.

Close all exterior doors and windows and turn on your kitchen and bathroom exhaust fans. Then open a nearby hot water faucet until you hear the gas burner in the water heater ignite. After a minute, move a smoking match around the edge of the draft hood (Photo 7) on top of the heater. The smoke should be drawn up the vent pipe. If the smoke doesn't draw, the fumes from the burner aren't venting. Turn off the gas to the water heater and call a licensed plumber to correct the problem.

Check for leaks

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Photo 9: Look for bubbles at connections

Turn on the gas and check connections for leaks by brushing a 50-50 mixture of dishwashing liquid and water over the joints. If the mixture bubbles, you have a leak. Tighten or reconnect joints that leak. Wipe the joints dry when finished. Call the plumbing inspector to check over your work.

Follow the how-to advice that accompanies the photos to make sure the connections are tight.

Light the pilot light

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Photo 10: Use a lighter to light the pilot light

Light the pilot light according to the manufacturer's directions. (For electric water heaters, turn the power on at the main panel after the electrical inspector checks your work.) Finally, set the temperature to 120 degrees F., following the installation instructions.

Light the pilot light in the new water heater and adjust the temperature setting.

How to install an electric water heater

Installation Details for Electric Water Heaters

First turn off the power to the water heater at your main electrical panel. Then follow the same draining procedures as for a gas water heater.

When the water heater is drained, disconnect the electrical wires from the screw terminals under the access panel, which is usually located near the top. (If you don't have electrical experience, hire an electrician to handle all the electrical wiring.)

Follow the manufacturer's instructions for wiring the new water heater. If the new water heater is shorter and the old wires won't reach, surface-mount a 4-in. x 4-in. x 1-1/2 in. metal electrical box on the wall or ceiling nearby, run the old wires to the box, and then run a new section of armored cable or electrical conduit to the water heater. Check the instructions and make sure the rating of the old fuse or circuit breaker is high enough to handle the new water heater. In addition, the circuit should have a shutoff switch within sight of the water heater.

Call your local electrical inspector before you begin the job. You'll probably need a permit. Then, when you're finished, have the electrical inspector check your work.

CAUTION: Aluminum wiring requires special handling. If you have aluminum wiring, call in a licensed pro who's certified to work with it. This wiring is dull gray, not the dull orange that's characteristic of copper.

Video: How to Dispose of a Water Heater

Jeff Gorton, an editor at The Family Handyman, will show you how to remove a water heater and dispose of it. He will also show you the easy way to carry a water heater out of your home, even if you are working alone.