What Is a Water Heater Sediment Trap?

Many kids (and even some adults) love filling their pockets with gravel, twigs and other surprises while on a walk or playing outside. The sediment trap for your water heater is like your children's pockets, except it's made of metal. You may even hear plumbers call this trap a “dirt pocket.”

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Your water heater sediment trap collects debris before it enters your appliance's gas chamber. Find out why this is important in this handy post about water heater traps.

What Is a Sediment Trap for a Water Heater?

A sediment trap is a small pipe connected to your water heater. This pipe behaves as a filter for your water heater. Tiny pieces of debris, such as dirt or metal shavings, can enter your water heater through the plumbing system. These particles, though small, can damage your appliance. Traps help stop debris from collecting in a sediment basin at the bottom of your water heater.

You may also hear a sediment trap called a drip leg, but technically, these are two different parts. Drip legs help capture condensation from gas piping and aren't always required in homes with dry gas. Sediment traps collect appliance-clogging gunk from the gas line that can damage your water heater.

What Does a Sediment Trap Do in a Water Heater, and How Does It Work?

Gravity matters when it comes to the location of your water heater's sediment trap. Typically, a sediment trap must be installed on the gas line below the shutoff valve for your water heater. The trap must be placed near the water heater inlet. This helps give particles a convenient place to settle so they don't continue traveling through your appliance.

A water heater's gas flow gets directed in a downward direction when a trap is installed. This makes it harder for sediment to get into your water heater. Imagine trying to throw pieces of dirt into a moving box fan. It would be difficult due to the airflow of the fan.

Sediment comes from different sources. When your water heater is installed, the plumber may need to shave or cut parts of your appliance. This can lead to tiny metal shavings in your pipes. Debris can also come from the ground when new pipes are installed that lead to your plumbing system.

Hard water can also cause debris buildup in a water heater. High levels of magnesium and calcium are hard to dissolve and may lead to rust or corrosion over time. The heating process can make these minerals more noticeable. A plumbing company may recommend getting a whole-house water softener to support your trap if hard water is a problem.

Regardless of how debris or gunk finds a way into your water heater, any type of sediment can cause problems. Particles can rub against the components of your appliance, eventually leading to cracks and leaks. Debris buildup can also result in clogs or blockages that make it difficult to access hot water in your home.

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Are Sediment Traps Required for Water Heaters?

Water heaters and other gas appliances typically require sediment traps, but exceptions exist. You might not need a trap installed if you have an illuminating appliance. Illuminating appliances are appliances that have visible flames while in use. Gas dryers and ranges may not need traps, either.

Many water heaters feature a built-in sediment trap. If yours doesn't, a professional might suggest installing one below the appliance shutoff valve near your water heater's inlet. This helps protect your appliance and can also keep you from failing a home inspection. Many inspectors check for sediment traps when they examine your plumbing system. Codes vary by state, so check with a plumbing expert if you have questions about compliance.