Troubleshooting Heat Trap Problems in Gas and Electric Water Heaters

Heat traps play a crucial role in maintaining the efficiency of water heaters by preventing the reverse flow of hot water, which can lead to unnecessary energy loss.

However, there are several heat trap problems that can reduce the efficiency of your water heater.

These issues include rattling noises, flow restrictions, thermal expansion through pipes, and energy loss.

Understanding and addressing these issues with the heat traps is essential for the smooth operation of your water heater.

Understanding Heat Traps in Water Heaters

Many modern water heaters, especially energy-efficient models from brands like Bradford White and AO Smith, are equipped with heat traps.

These heat traps come in two common types: the flapper-type and the ball-type. Each of these designs serves the same purpose—stopping hot water from flowing back into the tank—but they work in slightly different ways.

Heat trap nipples are typically located at the top of the water heater. The cold water line, marked by a blue ring, is connected to one nipple, while the hot water line, marked by a red ring, is connected to the other. These heat trap nipples are often factory-installed, making it relatively easy to locate and identify them when inspecting for heat trap problems.

The ball-type heat trap features a floating ball inside the nipple. When hot water is in use, the ball stays in place, blocking the reverse flow. However, when cold water enters the tank, it pushes the ball down, allowing water to flow into the tank. This design helps prevent heat loss by maintaining the correct direction of flow through the system.

Unfortunately, issues can arise with both ball-type and flapper-type heat traps, leading to problems that require attention.

Common Heat Trap Problems and Their Causes

There are several heat trap problems that can affect your water heater. These include thermal expansion (also called thermosyphoning), flow restrictions, and rattling noises. Each of these issues has different causes and solutions.

Thermal Expansion and Thermosyphoning

Thermal expansion, also known as thermosyphoning, occurs when hot water rises through the tank and enters the cold water line, which is supposed to carry only cold water. This is a clear indication of a heat trap problem, as it leads to wasted energy and poor performance.

One of the easiest ways to detect thermosyphoning is by feeling the cold water line near the water heater. If the pipe feels warm to the touch, hot water is flowing into it due to the combined effects of thermal expansion and convection. This can lead to significant energy loss, as the heater must work harder to maintain the desired temperature.

Thermal expansion occurs because water inside the tank naturally expands when heated. As the water rises, it can travel upward into the cold water pipe, creating inefficiencies in the system. The heat trap problem can be further compounded by convection, which causes the warm water to rise and flow into the cold side.

Several solutions can address this heat trap problem. Some plumbers suggest removing the plastic cap from the ball-type heat trap, but this can lead to new issues, such as noise, flow restrictions, and even blockages in the system. Additionally, removing the cap can affect the dielectric properties of the heat trap, which are designed to resist corrosion. For a more effective solution, some recommend bending the hot water pipes downward by at least 200 mm to prevent the thermosyphoning process. If this isn’t feasible, installing a non-return valve can help stop the reverse flow, though it may increase flow resistance.

Flow Restrictions in Heat Traps

Another common heat trap problem involves flow restrictions, which occur when the ball inside the ball-type heat trap gets stuck. This can happen due to poor installation, such as sloppy soldering of the pipe to the tank, which can cause the ball to become lodged in place.

A stuck ball prevents water from flowing freely through the system, reducing the efficiency of the heater and potentially causing other problems. In some cases, flow restrictions can lead to the complete failure of the heat trap, leaving the system vulnerable to heat loss.

To fix this problem, the first step is to check the ball and see if it is obstructed. If the ball is stuck, it may be necessary to loosen it using a screwdriver or other tool. In some cases, replacing the ball-type heat trap nipple with a flapper-type valve may be the best option, as flapper-type valves are less prone to flow restrictions.

Rattling Noises in the Heat Trap

A particularly frustrating issue with the heat trap is the rattling noise that can occur when the water heater is in use. This noise is caused by the ball inside the ball-type heat trap vibrating as water flows around it under pressure. The sound is especially noticeable in systems that use recirculation, where water is constantly moving through the pipes.

The rattling noise is a direct result of the ball’s movement inside the nipple. As water flows through the system, the ball vibrates, causing it to hit the sides of the nipple and create an annoying sound. This can be disruptive, particularly if the water heater is located near living spaces.

To address this problem, the solution is usually to replace the ball-type nipple with a flapper-type valve, which operates quietly and prevents the vibrations that lead to rattling. Installing a rubber-flap valve is a simple and effective fix that eliminates the noise without compromising the function of the heat trap.

Final Thoughts

Heat traps are an essential component of modern water heaters, helping to conserve energy and maintain efficiency. However, like any other part of the system, they are prone to problems. Issues such as thermal expansion, flow restrictions, and rattling noises are common heat trap problems that can be fixed with the right approach. By addressing these problems promptly, you can ensure your water heater operates smoothly and efficiently for years to come.

If you’re experiencing issues with the heat traps, consider consulting a professional plumber to assess the situation. Whether it’s fixing a stuck ball, replacing a faulty nipple, or addressing thermal expansion, the right solution can improve your water heater’s performance and reduce energy consumption.