Water Heater Heat Traps – Do They Work?

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Back in the day, a loop of copper tubing functioned as a heat trap for your hot water heater. These days, many water heaters include a more complex heat trap, and you can easily buy and install one in your existing heater. But how do they work, and are they worth the extra investment?

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How Does a Heat Trap Work?

heat trap nipple ball typeTraditional heat trap loops (sometimes referred to as goosenecks) take advantage of thermal convection. Hot water will rise and cold water will sink. By adding a U-shaped dip in the pipeline, the hot water gets stuck at the top of the loop while the cold is able to pass through the dip and enter the tank.

Although there are some minor variations in design for nipples (ex: balls vs flaps), the functionality is the same. Two small fittings are installed where your pipes enter and exit the tank. A Teflon ball sits in the fitting for the hot water outlet, while a polypropylene ball sits in the one for the cold water inlet.

When your water heater is in standby mode (i.e. you’re not drawing water), the balls rest in from of the valves and prevent heat from escaping (convection). As you turn on a hot water tap, the balls are lifted out of their seating to allow unobstructed flow and drop back down when you turn the tap off.

Do I Need a Heat Trap on my Water Heater?

Using either a heat trap loop or heat trap nipple can reduce wasted heat by as much as 60 percent. That really adds up when the bills come in. In addition, many state and local ordinances now require heat traps.

Another advantage to using nipples is that they’re dielectric, meaning they reduce the amount of corrosion to a steel tank when connected to a different metal (such as copper). Considering the relatively low cost for heat traps and simple installation, there’s no reason you SHOULDN’T. It may even extend the life of your anode rod.

How Difficult is it to Install a Heat Trap Nipple?

heat trap nipple installNipple kits are widely available online and at most hardware stores that carry water heater parts (such as anodes). We suggest investing in Rheem heat traps, although other brands such as AO Smith and Bradford White are also good. Installation is incredibly easy.

Shut off your tank and drain it by about two gallons. Remove the connection nuts from the existing nipples and apply some teflon taped to the trap nipples for some extra insulation and a better seal. Then you can simply insert the trap nipples and reconnect everything. The whole process can take as little as five minutes, excluding drainage time.

Heat Trap Problems

No component will be without issues, and water heater heat traps are no exception. Many plumbers prefer to bend pipe into goosenecks instead of buying prefabs to reduce the risk of blockage. Heat trap loops can also fail if not at a minimum diameter.

Problems with nipples are more common if you have a recirculation loop installed. The most common of these is noise from the balls. Flap models are quieter as a rule and are less likely to cause a reduction of water flow by getting stuck.

Improperly installed heat traps may also cause leaking at the connection at the top of the tank. Most often, retightening and/or adding a bit of teflon tape will solve the issue.

The good news is that heat trap nipple removal is just as easy as the initial installation, and you can often fix problems yourself. As blockage is most often caused by sediment or algae growth, regularly flushing your hot water tank and checking the anode rod for signs of decay will make these issues less likely.

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  1. I have a question – Is it advisable to remove the heat trap totally when installing a new water heater tank? An installer advised that to avoid flow/pressure and debris problems in the future and said that the heat loss problem without the heat trap will be minimal in terms of gas bill. Your advice? Thank you.

    • You really could go either way. I believe the benefits are worth it especially since heat trap nipples are easy to replace if there ever is an issue. A lot of plumbers advocate using longer flex lines (or copper tubing in an upside down “U” shape) to create a natural heat trap.

  2. One of the balls in the heat trap is getting stuck in the wrong position and restricting hot water flow. To get normal flow the water main is closed and the system (not the tank) is drained, buy opening a faucet the stuck ball will now release. Full pressure will resume when the main is opened. Leave a faucet open while opening the main. The heat trap and tank were installed in 2002.

    • This is fairly common failure point of a heat trap nipple with the ball inside. Simply replace it or switch to a nipple that uses a flap instead of ball.

  3. There was No indication in instructions on which direction to install my heat trap nipples on my 75gal hotwater heater. Did it matter? If so, how can I tell? I guessed and put black ball inside heater.

    • There should be an arrow on a dielectric nipple which shows the direction of water flow. So for cold, it should point into the tank. Hot, arrow points out of the tank.

      • I have replacement heat trap nipples for my Rheem water heater. There is no arrow or any indication of direction on the heat traps. There is a groove on the outside of the nipple, but what it signifies is unknown. One end has pipe dope already applied.

    • Yes it should be fine if you’re using a reciruclating pump. With a “gravity” type recirculating loop, you’d need to remove the heat trap.

  4. I have had the cold water heat trap stick close repeatedly and thought it calcium buildup. On average, it would occur monthly, but the last time was a week between episodes. I had been clearing it by opening the cold water connection and stabbing a screwdriver into the tank connection.
    Draining the tank produced no calcium.
    The heater was ten years old, and as a precaution I replaced the heater today.
    I pulled the dip tube and there was no calcium build up. I turned it upside down, and something slid to the opening. It was not ball shaped, but more like a likeness of a water drop with a pointed tail. The tail would be the part that filled the valve opening.
    Is this a new kind of heat trap?

    Hate to think I spent money and hours on a plastic valve being stuck.
    The old heater was an american standard.

  5. I have Rheem water heater and Watts recirculating pump. Not functioning well. Watts says recirculator should reduce time to hot water by half. Only getting 30% reduction. Also, the speed of hot water varies, sometimes it comes quickly, other times, I fill a bucket. Watts says it’s a compatibility issue and possibly the heat trap. They say to remove heat trap. Contractor doesn’t want to remove for maximum efficiency. Rheem is giving various responses. Any suggestions?

  6. My flex connections with rubber washer seals leaked due to the plastic cap style heat traps installed in the nipples on my new water tank. I removed them and the leak was fixed. Technically you are not advised to use tape or dope on the nipples when using flex connectors as the rubber washer does the sealing and NOT the threads, so although tape or dope may have worked initially to stop the leak, I worried that the leak may return after time since the threads are not designed to seal on flex connectors, and the leak may go both ways, up and down the threads on the flex connector.

  7. I purchased two twenty four inch half-inch to half-inch flexible hoses for connection to the tank water lines (with braided shield), I made a loop trap connection to each of the tanks water connections.

    The hot-water heater is in the basement and the use of hot water taps are on the main and second floors.

    Prior to the installation of the loop trap for convection loss, I noted that convection within the hot water pipe was allowing hot water to go straight up. Given 22 hours a day of not using hot-water, that convection loss was costing money for nothing. I did note that I had some heat-loss traveling back through the cold water connection. Cost was about $50 for the two hoses. I bet I recover that hose cost alone in the summer months. Recall that extra heat in the house in summer has to be cooled by the central air-conditioning system

    The flexible hose has at least a 10 year lifespan. If I have to change the tank, I will need some teflon tape for the tank connections and just to redo the electrical connections.

    Ideally, it would be great to have a on-demand hot water heater under each sink to supply the taps and showers. One for each bathroom.

  8. I have a GE profile 80 gal electric water heater with heat traps inside the tank (i.e. not in the nipples). The cold ball is sticking in closed position. I would like to service the dip tube and heat trap but cannot see how to remove either the heat trap or the dip tube when the nipple is unscrewed – both are further down inside the tank. Any help on how to remove this type of heat trap w/dip tube? Is there just a sufficient buildup of crud that I cannot see the tube and trap just pops out? Tank is 20 years old, with dual heating elements. GE model se80t12a. Thanks for your time!

  9. If you have a 20 year old water heater turn off the water then pull the magnesium anode. If the anode still has at least 25% magnesium go ahead and REPLACE the magnesium anode. Water heaters will live indefinitely if you check the magnesium anode once very 5 years and replace if needed or just replace it once every 5 years the labor will be the same. Magnesium is readily recyclable just like any other metal.

    If the magnesium anode looks like tire that is worn down to the cords what you need is a NEW water and buy 1 or 2 spare anodes whilst you are at it. With a spare aode around replacing it is easy.


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