Sediment and Hot Water

All water that enters into a water heater contains natural minerals of some kind. Heating the water causes the minerals to separate and fall to the bottom of the tank. Usually this sediment build-up is made of calcium carbonate. One sign of sediment build-up is a sulfur (or rotten-egg) smell around your water heater. With gas water heaters, sediment problems may cause the entire heater to become noisy while on.

In gas water heaters, sediment rests on the burner plate inside the tank; the burner plate sits directly over the flame underneath the tank. Sediment on the burner plate inhibits the transfer of heat to the water, so it takes longer to heat the same amount of water. Sediment also traps the heat underneath it which can cause the glass lining—found in every water heater tank—to melt once it reaches 160° F. The metal at the bottom of the burner plate can also warp due to the excess heat. Either of these problems can lead to leaks.

Bacteria problems in water heaters.

Another problem associated with sediment build-up is bacterial growth inside the tank. The bacteria in water heaters are not the typical disease-causing bacteria. Rather bacteria problems in water heaters lead to a corrosion of the water heater tank lining through oxygenation. The sediment build-up itself, combined with the added bacterial problems, can cause serious damage to a water heater. The odor of sulfur or rotten-eggs around a water heater is a symptom of bacterial problems. This odor should not be confused with that of a potential natural gas leak in gas water heaters, which may have a similar smell. Either problem is serious; they should be repaired immediately.

Controlling sediment build-up.

One way to slow sediment build-up is to use a softening agent, although this method does reduce the life of the anode rod (see Anode Rods). Another way is to adjust the temperature and pressure of the water. Both high temperatures and high pressures cause sediment to form in the tank faster. Sediment develops rapidly in temperatures of 140° F or higher. The optimum temperature for a water heater is 130° F. At this temperature, sediment build-up slows, but the water is still hot enough to kill harmful, disease-causing bacteria (for example, the bacteria that causes legionnaires’ disease flourishes in temperatures up to 115° F). To check the temperature, simply fill a container with hot water from any sink. Make sure it is as hot as it can get. Use a meat thermometer to measure the temperature. To adjust the temperature on a gas water heater, find the ON/OFF PILOT control knob at the bottom of the tank. There is often a smaller adjustment knob in the center of the ON/OFF PILOT control which reduces or increases the size of the flame on the burner plate. For electric water heaters, in order to reduce high temperatures, you will have to install a low-watt density heating element in the tank. The low-watt density heating element has twice the surface area as a normal heating element; this means the low-watt element doesn’t have to use the high temperatures that a normal element does to achieve the same water temperature in the tank. Lastly, if your water pressure inside the house is over 50 psi, then have a pressure reducer installed by a plumber for your water heater.

The curved dip tube flushing method for removing sediment.

Most water heaters will have a standard straight dip tube connected to the cold water inlet. A straight dip tube is simply a straight pipe that sends cold water from the cold water inlet to the bottom of the tank. The force of the water entering the tank cleans the small area at the bottom of the water heater directly underneath the dip tube, but leaves the rest of the dome-shaped bottom of the water heater covered with sediment. Unfortunately, draining the water heater with the drain valve outside the tank will removes very little sediment. But installing a curved dip tube will greatly reduce the amount of sediment build-up at the bottom of the tank. A curved dip tube is exactly the same as a straight dip tube except for the curve at the bottom of the pipe. This curving of the pipe sends the new cold water entering the tank swirling around the dome-shaped bottom. The curved end on the dip tube can be pointed in any direction. A curved dip tube not only helps prevent sediment build-up, it can also help break up and flush sediment from the bottom of the tank. Once the curved dip tube is installed, open the drain valve and allow the swirling water to flush the sediment out the drain valve for five minutes. Open the drain valve at the bottom of the water heater. It looks like a normal hose bib in most cases. INSTALLATION: To install a curved dip tube, first unscrew the cold water outlet line. Insert the handle of a plastic set of pliers in the inlet of the tank. Twist and pull up at the same time to expose the dip tube. If the tube is difficult to remove, scrape off any rust on the tube or in the inlet. Once the dip tube is completely removed, take the new curved dip tube and mark the direction the curved end of the tube is pointing on the nipple (the small plastic pipe connecting your new dip tube to the cold water outlet). Wrap the threads of the nipple with Teflon tape eight times. Then, insert the curved dip tube making sure the direction the curved bottom of the tube is pointing in will cause the desired swirling motion of water at the bottom of the tank (the curve should be running parallel to the lining of the tank). NOTE: If unsure, hire a plumber to install the new curved dip tube. Also, if you have a plastic drain valve, ask the plumber to install a ¾ inch ball valve to replace the plastic one. A ¾ inch ball drain valve has a much larger opening to flush out sediment.

Dissolving sediment chemically.

You may buy a chemical descaler called Mag-Erad from A. O. Smith Inc. Before using the product, however, you must first drain the water from the tank completely. If you have a gas water heater, you must turn off the gas even though the instructions may say to leave the gas on while using the product. Nevertheless, if you leave the gas on while using the product you will damage the flue. With electric water heaters, you can use the product without problems. Have a curved dip tube installed by a plumber and have him flush the water heater in the way described above.

Removing sediment in commercial water heaters.

As with residential water heaters, some signs that a commercial water heater has a sediment build-up problem are excessive noise and/or a foul odor. Removing any sediment in a commercial gas water heater will save approximately 5% on your energy bill; for commercial electric water heaters the removing sediment does not affect the cost of energy much. To remove sediment from a commercial water heater, first turn off the gas or electricity. Turn off the water to both the hot and cold lines as well as any re-circulating system connected to the water heater. After this, open the T&P (temperature and pressure) valve; this will relive the pressure in the lines and allow the water to drain through the drain valve. Before opening the drain valve however, first attach a water hose. After opening the valve, if no water comes out, then sediment is most likely blocking the drain. You will have to completely remove the drain valve itself, and then break up the sediment using a screwdriver. If there is any rust, remove that as well. Use a drain pan at the foot of the open drain valve port and continue to flush as much sediment from the open port as possible. If you wish to completely remove all the sediment, you should hire a professional plumber.