A Heat Trap is a device or, method of piping used to limit the loss of heat from a water heater by convection or, thermosyphoning up through the pipes entering or leaving the water heater. Many codes require the installation of heat traps to save on energy costs.
The most common method used is to install heat trap nipples on the inlet and outlet of the water heater. A heat trap nipple typically has either a ball or, flap built into the nipple that blocks the flow of heat up out of the water heater into the pipes, yet moves out of the way when hot water is turned on allowing water to flow unobstructed. Many times water flowing though a heat trap nipple can generate noise with either the ball rattling in the flow or, the flap making a buzzing noise. Typically heat trap nipples are also dielectric which means they limit corrosion of the steel water heater tank which can be caused by connecting dissimilar metals to the water heater such as copper.
Another less common heat trap can be made with pipe installed in a â€œUâ€ shape where the heat attempting to escape is forced to flow downward through the â€œUâ€ before it is allowed to go upward again. Since heat rises, this piping method stops the heat loss without the use of any check valve. There are minimum dimensions for this heat trap which must be followed in order for the heat trap to function properly.