You can take your time with some handyman projects, coping with setbacks and unexpected complications as they come. Not so when replacing a water heater. At a minimum, you will be without hot water until the job is completed. In fact, you also may have to shut off the water to your entire house - hot and cold - during much of the project.
As a licensed plumber, I install dozens of water heaters each year. So the Club asked me to show you the tricks that make the job go smoothly.
My first piece of advice is to find out what your local building department requires and prefers when changing a water heater. For instance, some local codes do not permit flexible copper or stainless - steel - jacketed supply lines. Others prohibit flexible copper gas lines because sulfur in some gas creates line - clogging scale in the tubing. Use black iron pipe.
Second, don't assume that you should install the new water heater just like the old one. I can't tell you how many times I've removed old water heaters that were installed wrong. Sometimes the gas line lacks a waste tee at the heater. Other times the exhaust hood or flue duct is undersized.
The most common mistake people make when they replace a water heater is to cut the supply lines too close to the old heater and assume they will be able to reuse the existing lines, valves and ducts. It will cost you a little more for parts, but trust me: It is easier to replace a heater if you give yourself room to replumb it.
The installation shown here is typical of what I find in many homes. The old heater did not have corrosion - resistant dielectric nipples at the hot - and cold - water ports. I had to raise the shutoff valve to install dielectric nipples, threaded couplings and short tubing risers on the new heater. I also replaced about 5 ft. of flue duct because the old transition fitting was backward, going from female to male rather than from male to female.
To conserve energy, a water heater should have heat traps at both the cold and hot ports so the heat does not migrate out of the tank when no one is drawing hot water. The water heater shown here has a check valve on the cold side - a hollow ball that rises in the dip tube and blocks the inlet when cold water is not flowing into the heater. The hot - water outlet had its own check valve. If it hadn't, I would have installed a dielectric nipple with a built - in check valve or trapped the heat with a thermal loop fabricated with four elbows and short sections of rigid tubing. Some people don't like check - valve - equipped nipples because they can produce an annoying rattle. Check valves located inside the tank are quieter, but thermal loops are best because they have no moving parts.
Before you begin the job, be sure you have everything you will need. To reconnect the water lines, you will need a new 3/4 - in. ball valve for the supply line, 3/4 - in. copper tubing, 3/4 - in. threaded - to - sweat copper couplings, a couple of 3/4 - in. sweat couplings (the slip type if you can't raise the lines), a pair of dielectric nipples, 95/5 solder, flux, Teflon tape and Teflon paste (for the gas line). It's also good to have duct fittings and self - tapping sheet - metal screws to restore the flue.
Out with the old
Begin by turning off the gas at the shutoff valve on the line to the water heater. For added safety, I also install a cap on the end of the gas line. Turn off the water at the main and drain the water from the hot and cold lines throughout your house by opening all of the faucets indoors and outdoors. Start with the highest fixture and finish with the lowest.Carefully drain the hot water from the heater by attaching a hose to the drain valve. If sediment blocks the valve, you may have to clear the valve with a coat hanger.
In with the new
I'd like to emphasize a few tips for avoiding common mistakes.
Sweat short sections of copper tubing onto the threaded couplings before you screw the couplings to the dielectric fittings to avoid melting the fittings' plastic linings with your torch.
Sweat the valve as quickly as possible so the heat doesn't damage the seals. You also can wrap the valve body with a damp rag to prevent it from overheating. Make sure the heater is full of water before you ignite the burner or turn on the power and be sure to test the temperature of the hot water at the faucet nearest to the heater. To avoid scalding burns, it should be no higher than 120 degrees F.