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Energy-Efficiency Enhancing Technologies: Heat Traps

A heat trap prevents heated water in a storage tank from mixing with cooled water in pipes, a process called thermosiphoning. It does this by preventing hot water in the outlet line from getting back into the tank as it cools and also by preventing hot water in the tank from circulating out into the cold water inlet line.

Several types of heat traps are available with the most conventional utilizing either a plastic or metal ball. Plastic heat traps are considered to be those devices which are integral to the tank design in contrast to metal heat traps which attach to the inlet and outlet pipes. In one style, a floating plastic ball blocks the cold water inlet. The buoyancy of the plastic holds the ball in place until water is drawn. The force of water is strong enough to push the ball out of the way as water enters the tank.

A second option uses the ball to block the hot water outlet. The ball is denser than water so its weight seals the outlet until hot water is drawn and the water pressure lifts it out of the way. Other designs include U-shaped pipes, flexible seals, flaps, springs and other mechanisms.

Some critics argue that heat traps are noisy and cost more than the energy savings can justified.