How to Replace a Hot Water Heater (Tank)

replacing a hot water heater

If you have a water heater in your home, there's a good chance it's a tank unit. This type of water heater has been around for years and is currently the most popular water heating choice on the market. They provide many advantages over alternatives (like on demand water heaters).

One disadvantage is that in order to provide you with hot water when you want it, tank units need to run constantly, even while you sleep or are not even home. So before we get into the tutorial, I would like to recommend that you choose an energy-efficient water heater. It will pay off in the long run, and is a good way to help conserve resources. Whether you are installing an electric or gas unit, this guide will give you the knowledge you seek on how to replace a hot water heater.

Mythbusters Water Heater Explosion

Before we proceed, watch this awesome video from Mythbusters. In hilarious and impressive fashion, it explains the dangers of water heater modifications which could lead to unsafe temperatures that create too much pressure. This is why there are safety functions built into water heaters today, one of them being the pressure relief valve. Enjoy this cool segment before proceeding to read up on how to replace a hot water heater.

Also, it should go without saying that you need to match the fuel type to whatever setup you have existing at your home. There are converters from propane to natural gas, and vice versa, that you can purchase separately, but most manufacturers today provide fuel specific water heaters from the factory, keeping things simple... always a great general rule of thumb.

I will cover steps for replacing your water heater in 3 parts:
  1. Removing the old unit
  2. Installing an electric unit
  3. Installing a gas-fueled unit

How to Remove the Old Water Heater Unit

Before you start, if you're playing with gas, you don't want to end up playing with fire. It would be a good idea to keep a fire extinguisher nearby, just in case. Some of these steps apply to gas units, some apply to electric, but most will be general enough for both:

  1. Turn the gas valve to the off position. This valve would be the one close to the wall usually with a small red handle, not the one on the front of the heater. If it is electric, turn off the circuit breaker for the room you are working in, and disconnect the power to the tank.
  2. Verify the gas line is not leaking. To do so, watch the pilot light burn out. If it stays on, it means the unit is still getting gas, and the valve is not closing the line. If this occurs it would be a good idea to turn off your gas at the meter. you may have to re-light other pilots in the house but better to be safe than sorry.
  3. Turn the pilot to the off position.
  4. Disconnect the exhaust ducts from the tank (for gas-fueled only), This may require the use of a 1/4 or 5/16 inch socket to disconnect the first element of the vent from the top of the heater.
  5. Shut off the water valve at the inlet, usually found above the tank itself.
  6. Release the water by connecting a hose to the valve at the bottom (looks like you hose bib outside), and opening it just like turning on an exterior hose. Run the hose line to a drain or out the window being careful to secure it place to keep from getting scalded. A gallon of water weighs around 8 lbs, so if you want to move a 50 lb tank with water in it, you better be at the top of your crossfit game. Much easier to drain it, first!
  7. While you wait for the water to drain, disconnect the tank from the gas line. In between you gas valve and your water heater is a flexible gas line called a gas flex. This line does not generally need to be replaced so use a pipe wrench to disconnect it from the gas valve on the front of the water heater. Use a second wrench with the other hand to prevent counter-torque from wreaking havoc on your gas line.
  8. Disconnect the water lines (both in and out) and watch the magic as gravity takes over and the tank evacuates the water at a much more rapid pace.

Once the water has completely drained out, you should be all set to remove the tank.

General Installation Tips

Will I need to know how to use a torch for soldering? Water heaters can be hooked up to any water pipe available, but any plastic water pipe needs to have water flex connections at least 18" long to keep from overheating the pipe. These water flexes are made of copper and have threaded connections on both sides, so no soldering is required in this instance. It is Possible to get water flex connections that are solder connection on one end and threaded on the other, if you are tying into an existing copper line, so some soldering will be required for those. There are more instructions on soldering later in the article*.

The pressure relief valve outlet may require some soldering, but that can typically be run with PVC pipe and a male adapter instead (the valve threads into the water heater, so no soldering there).

How to Install an Electric Tank Water Heater

Installing an electric water heater is a pretty straight-forward process, and you should follow the instructions that certainly came with your purchase, but nevertheless, the basic steps are outlined here:

  1. Move your tank into position.
  2. Ensure that the drain valve is closed tight.
  3. Connect the supply line with the shutoff valve to your water heater inlet (should be marked as Cold, or have a blue ring around it) followed by the line out connection. Remember, this may require sweat soldering. It's not a bad idea to color code your fittings. Blue for the supply line in and red for the hot water line out. (if you have to solder, there are instructions below*).
  4. Once both the connections are tight, turn the main water supply on and watch and wait as the tank fills up, keeping your eye open, checking for leaks. If you feel like it's near full, you can verify by going to the top floor of your home and turning on a tap. If there is no steady flow of water, you tank is not yet full. (full or not expect some spitting and hissing as the air in the water lines is replaced with water)
  5. Remember, you still want the power off at this point.
  6. Connect the electrical supply following your instruction manual, closely.
  7. Replace the access plate when finished connecting
  8. To access the thermostat, you will probably need to remove a plate. You can change the temperature with a screwdriver, and the recommended temperature for your hot water is about 120 degrees.
  9. Turn the power in your utility room back on using the circuit breaker.
  10. Now you're all set. You may need to reset your thermostat by carefully pressing the red button usually located on the top of the thermostat itself. And now you're in business!

How to Install a Gas-Fueled Tank Water Heater

Whether you are interested in installing a propane water heater, or more commonly, a natural gas water heater, the steps will be very similar and will both be outlined here:

  1. Move your tank into position.
  2. Ensure that the drain valve is closed tight.
  3. Connect the water supply line with the shutoff valve to your water heater inlet (should be marked as Cold, or have a blue ring around it). Again, you may have to solder, but maybe not. We recommend using teflon tape for better connections with the supply line and the water heater. Connect to the hot water line out (if you have to solder, there are instructions below*).
  4. Connect the Gasflex to the water heater valve on the front of the heater. The side that hooks into the heater will require Teflon tape or pipe dope, but the connection on the gasflex side is a "flared" connection and does not.
  5. Connect the tank to the ductwork leading to the draft hood that vents out the water heater. This may require the use of a 1/4 or 5/16 inch socket depending on your heater brand.
  6. Turn on the water supply line, and the tank should fill up. If you feel like it's near full, check a faucet on your top floor. If there is no steady flow of water, you tank is not yet full. (full or not expect some spitting and hissing as the air in the water lines is replaced with water).
  7. Double check that your water heater valve is set at the "Off" Position, and turn your gas valve on.
  8. Follow the instructions for setting the Pilot. Some are manual, others are autoamtic. Ignite the pilot light, set the temperature (120 degrees, or so) and you're in business!

Soldering instructions*

With options mentioned before the tutorial guide, you can avoid soldering, but for some men they just like to solder, but often times it is necessary, so this part guide is for them. In some cases you will have to remove and replace the shutoff valve to make things fit right with your new installation, or manipulate the length of the pipe for a better fit. If either of these are required follow the steps below BEFORE turning on any water or gas lines.

  1. When using Galvanized nipples to connect your heater to copper or brass, a Dielectric Union is Required to prevent "Galvanic Corrosion" which is a corrosive reaction created through acidic electrolysis that leads to week and faulty connections. A simpler solution would be to thread a "waterflex" to the nipples coming from the water heater inlet and outlet. These flexible supply lines are created to isolate the corrosive reaction, eliminating the need for a Dielectric union. The other end can come in either another threaded connection or a solder connection depending on your application.
  2. Soldering Pipe takes some practice, but following a few simple rules will help to make your weld leak free. a) Clean your connections and pipe inside and out. This is usually done with emery cloth and wire brushes b) Use flux on both the inside of the fitting and the outside of the pipe. c) Don't turn your torch too high d) heat the fitting not the pipe. This will "draw" the solder INTO the fitting. (it's pretty cool to watch) e) Have a water bottle spritzer handy.
  3. Once your fitting and pipe have been cleaned, apply a nice coating of flux to both pieces and slide together.
  4. Unroll about 12" of solder from the roll and bend the end to form a hook shape leaving about 10 inches between you and the end
  5. Turn on your torch, being careful of your surroundings, adjust your torch settings to a medium flow. Because soldering works best with consistent heat, the area behind your fitting will get hot enough to burn. If you are soldering close to combustible materials, use a "Heat cloth" behind your fitting to prevent catching things on fire.
  6. Point your flame at the fitting side of your connection until about 1/4 of the flame's length is on the fitting
  7. Place the end of the solder that you previously bent, on the backside of the pipe right where the fitting and the pipe meet.
  8. working on a tank water heater
  9. Once the fitting becomes hot enough the end of your solder will liquefy and be drawn into the fitting. As soon as this happens slide the end of the solder all the way around the pipe.
  10. Sprits with water when complete for a quick cool down, and shut off your torch.
  11. Once all of you fittings have been soldered, turn on your water and check for leaks. If leaks are apparent repeat steps 4-9

Note: Pipe or fittings with water in them will NOT heat up enough to solder until the water is removed. If water is still draining to your location, take some crusts of bread and stuff them in the pipe. The bread should soak up the water long enough to solder your connection. Remember to remove the aerator from your faucet before turning it on or it will be filled with mushy bread (YUCK!).

Well, that's it! You should be good to go. Hopefully this has been helpful in teaching you how to replace a hot water heater. Remember, we have great deals on water heater parts, as well as accessories.

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