3 Common Water Heater Expansion Tank Problems

A water heater on a blue background.

When thinking about installing or replacing a water heater expansion tank, it is good to know about a few potential problems that are commonly experienced. If you must change out the tank, it is also important to have the necessary knowledge and tools before starting the project.

A pipe wrench, plumber's tape, old towels, and a flashlight are helpful items to have nearby, along with any instructions that may come with the expansion tank itself. To help eliminate future risks, make sure that directions are carefully followed and all parts are installed correctly.

1. Excess Water

When water is heated, its physical volume increases. The purpose of an expansion tank is to provide a place for the extra or bigger water to flow, so that it does not back up out of the tank into the main municipal water supply.

In this way, an expansion tank is similar to the separate radiator overflow reservoir on a car. If valves or gages are damaged, they may not properly regulate the flow in and out of the expansion, and excessive water build-up can occur. Dangers from this problem include explosions, water spilling out onto the floor and hitting electrical circuits or snuffing out the pilot light, and ruining the floor near the heater.

2. Condensation Problems

Sometimes there may be excess condensation on the outside of the water heater tank. This could happen if the expansion tank is holding too much water, or if the temperature setting on the heater is too high. Thick condensation can also appear in warm, humid climates when the tank is heavily or over-insulated. Smaller water tanks that are used frequently can also cause condensation problems because they have to be refilled with cold water more often than a larger tank.

As with overflow, condensation can be dangerous if it drips down onto electrical components. It may also drip to the floor and puddle, which can cause a mess, but may also aid the production of mold and mildew. Long-term condensation can also cause rusting outside the tank.

3. Valve Problems

Water heaters have many valves inside and outside the tank, and they must be in good working order so as to not damage the system. Valves and their related tubes and hoses can break, strip, or rust. Newer parts are generally of better quality, designed to hold up longer against rusting and gathering corrosion.

If the area has hard or soft water problems, take care to use any necessary treatments, so that mineral deposits do not collect inside the tanks and gum up the system. Clogged valves, hoses, and tubing can damage the tank and reduce water pressure.

And speaking of water pressure, check that the gauges and sensors of the tanks are set correctly to balance the local community standards. Average water pressure can change from block to block in a neighborhood, and this can make a difference to each tank's optimum settings. Proper settings keep the valves from working too hard and wearing out before their time.