It’s something we don’t really think about — until it stops working. When your shower gets cold, that’s when things heat up!

Amidst cries of outrage about cold water showers and cold water dish washing, we scramble to figure out what caused the water heater to stop working. But, before we talk about things that can go wrong with water heaters, let’s take a look at their simple, yet creative design and discover how it is they do what they do to make our daily lives more comfortable.



The majority of residential water heaters are storage water heaters. They are basically tall cylindrical tanks–sort of like a tall metal drum. They vary in capacity from about 20 gallons to about 80 gallons of water. Even though traditional water heaters don’t present a very dramatic appearance, the principles they use to supply abundant hot water to your home are pretty interesting.



water heater

                  photo credit: US Department of Energy


Storage water heaters are comprised of the tank and a couple of tubes, a series of valves, and a mechanism for heating the water. Storage water heaters are either electrical or gas operated. Here’s how all these components work:

  • Tank: The tank is made of heavy metal and is actually the inner component of the cylinder. It serves as a shell to hold the water. Tanks are often covered with some type of insulating material, a decorative “outer shell” and sometimes an additional insulating blanket-type cover.
  • Dip Tube/Cold Water Inlet: Cold water enters the tank at the top and flows through this tube to the bottom  of the tank. Because the water is cold, it stays close to the bottom of the tank where heating occurs.
  • Hot Water Outlet: This pipe is also at the top of the tank. Heated water at the top of the tank exits through this outlet and flows to areas where it is needed.water heaters
  • Shut-Off Valve: This valves closes off the flow of cold water into the tank.
  • Drain Valve: This valve is near the bottom of the tank and is used to empty the tank when servicing is needed.
  • Pressure Relief Valve: This valve serves to regulate pressure inside the tank.
  • Anode Rod: This rod, made of steel overlaid with either magnesium or aluminum, is suspended in the water of the tank to help reduce corrosion.
  • Heating mechanism: In a gas storage water heater, the heating mechanism is a gas burner and chimney system. An electrical storage water heater uses heating elements projecting into the interior of the tank to heat the water.
  • Thermostat: This device is a thermometer and a temperature-control device. Electric water heaters may have individual thermostats for each heating element.


water heatersStorage water heaters rely primarily on the scientific principle that hot water rises. Cold water enters the top of the tank through the dip tube or cold water inlet, flows through the pipe to the bottom of the tank where it exits the pipe, pushing the warmer water already in the tank upward.

The thermostat setting is usually between 120 – 180 degrees Fahrenheit. The thermostat should be set nearer the lower end of this range in homes with small children to prevent potential scalding injuries. As the thermostat monitors the temperature of the water inside the tank, it regulates the function of the elements (on an electrical water heater) or the gas burner (on a gas water heater) to heat the water accordingly.

Because heat rises, the hottest water is always closest to the top of the tank. When a hot water tap is turned on somewhere inside the home, the hot water exits the tank through the hot water outlet at the top of the tank and flows to the open tap.

What’s next?

Now that we have a basic understanding of the parts of a water heater and how it works, our next post will take a look at some things that typically cause water heater problems resulting in the dreaded cold shower.

Whether you have a malfunctioning water heater or a leaking faucet or a clogged drain, Knoxville Plumbing is here for you!

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In our last blog post, we covered how to prepare your sink in order to fix it and how to repair a compression faucet. The blog post will include the instructions on how to fix ball faucet, cartridge faucet, and ceramic-disk faucet.

ball faucet

It’s easier to figure out if this is a ball, cartridge, or ceramic-disk faucet by looking at the inner mechanisms.

HOW-TO: Fix a Ball Faucet

  1. You have to buy a replacement kit because of the ball faucet has several parts that need replacing and specials. Don’t worry! You don’t have to replace the entire faucet and the kits tend to run at twenty dollars.
  2. You must unscrew the handle and remove it.
  3. You use your pliers to take off the cap and collar. Afterward, loosen and remove the faucet cam, washer, and ball. You’ll recognize it because it looks like a human ball and socket joint.
  4. You need to use needle-nose pliers to reach into the crevice and take out the inlet screws and springs.
  5. You should replace the O-rings by cutting out the old ones, rubbing the new ones in plumber’s grease, then installing them.
  6. You should install the cam washers, valve seats, and springs that are in your kit. It’s done in a reverse process from when you started the how-to guide.
  7. You can now put your faucet back together.

HOW-TO: Fix a Cartridge Faucet

  1. You should remove the handle by prying off the decorative cap and unscrewing it.
  2. If necessary, take off the retaining clip to get at the cartridge. It’s a plastic item that holds the cartridge and you can remove it with pliers
  3. When you have your cartridge in hand, pull it so it’s lengthened.
  4. You should remove the faucet to look for the O-rings.
  5. You should replace the O-rings by cutting out the old ones, rubbing the new ones in plumber’s grease, then installing them.
  6. You can now put your faucet back together.

HOW-TO: Fix a Ceramic-Disk Faucet

  1. You should take out the escutcheon by removing the handle. It sits directly underneath it.
  2. You should take out the disk cylinder, which will expose the neoprene seals underside.
  3. You should pry out those seals, cleaning them and the disk cylinder with white vinegar. Let it soak for several hours then see if you can still use it.
  4. You can now put your faucet back together, but be careful! At this point, you should test turning the water on because if it’s too forceful, you may crack the ceramic disk.