Water Heater Heat Traps – Do They Work?

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Categories Water Heating
Retain heat by adding a water heater heat trap — here’s everything you need to know.

Are you looking for a way to make your water heater more efficient? Are you tired of receiving a high energy bill due to escaped heat? Today, we’re all about water heater heat traps and whether they’re worth the investment.

Heat traps have become so essential that nearly all new water heaters have them. They’re simple and effective. Today we’ll take you through exactly how they work and if you could benefit from one.


What Are Water Heater Heat Traps?

The first heat trap invented was made of a basic copper tube shaped into a loop, that would trap the heat. Today, heat traps have evolved to become more effective.

They’re still simple constructions, sometimes consisting of a pipe formed as a valve or loop similar to the original one. But today, the systems incorporate small metal elements called “nipples” — a small piece of piping with either a ball or flap sitting on the inside.

You place the heat traps on the water inlet and outlet pipes. Here, they’ll prevent heat from escaping due to convection. You can install heat traps on gas-fueled or electric-powered water heaters.

How Do They Work?

There are, in general, two main types of heat traps. The traditional loop pipe and the newer heat trap nipple. Both restrict convection to prevent the heat in the tank from escaping.

Most storage tank water heaters have something called a dip tube. This is the cold inlet pipe leading the fresh water into the tank.

In a trapless system, as the unit heats the water inside the tank, it expands and begins to rise through the pipes.

Eventually, heat escapes through the plumbing. This results in wasted energy as the boiler now has to use more power to maintain the temperature of the tank. This turn of events is what we call natural convection, or thermosyphoning (1).

With a traditional heat trap, the inlet and outlet pipes are shaped into a loop, also called a “gooseneck.” The reshaped pipes trap the heat at the top while enabling the cold to pass through. As the hot water rises, the cold water will sink to the bottom where it’s heated.

As we mentioned briefly, newer variations of heat traps incorporate nipples. These are fitted with either a ball or a flap, which most experts now recommend. They’re reported to be more effective due to their small size, and also significantly quieter.

The two types work similarly. A Teflon ball or flap will sit in the fittings for the hot outlet while a polypropylene ball or flap will sit by the inlet. Teflon is used because it can withstand the corrosive nature of hot water.

As your water heater is resting in standby mode, the heat traps rest in front of the valves. Here, they prevent heat from dissipating through the plumbing. When you turn on the hot water tap, the flaps or balls lift, allowing for unobstructed flow.

Are They Worth It?

A loop or heat trap nipple will significantly reduce the amount of wasted energy, with some estimates at as much as 60 percent. If we look at this in terms of energy bills, you could save anything from $15 to $30 monthly (2).

Heat trap nipples also provide an added benefit. Most will create a dielectric union that may extend the lifespan of your anode rods. This connection is even capable of reducing corrosion inside steel tanks.

What’s more, heat traps have been shown to be so important that some states require water heaters to have them built-in. Many homeowners choose to retrofit their old unit rather than replace it.

As a bonus, heat traps are generally inexpensive and very easy to install. Even if you don’t want to do the installation yourself, professionals usually don’t charge much.

Common Heat Trap Problems

Heat traps aren’t exempt from problems. The most common issues that we see are rattling noise, thermal expansion, flow restrictions, and loss of energy. The cause of these problems is usually a poor installation or a faulty trap.

Let’s have a look at each problem in more detail, plus some solutions.

1. Thermosyphoning, Convection, or Thermal Expansion

Thermosyphoning is a problem that occurs when something’s wrong with the heat traps. It’s easy to spot since the cold water might run warm or even hot.

If there’s an issue with the heat traps, they lose their function and allow hot water to enter the cold pipes. If you think this is happening, try to feel the inlet pipe. If it’s hot to the touch, you know there’s a problem with at least one of the heat traps.

Some DIY homeowners might suggest that you remove the plastic cap. This is not recommended as the ball can then fall into the system and create noise or flow restrictions.

Doing this can also meddle with the dielectric effects of the heat trap. This in turn decreases the corrosive resistance of the anode rods, leading to rust in the tank.

The Solution

Remove the existing pipes and replace them with longer, more flexible lines. Then create a gooseneck heat trap and wrap the pipes with thick insulation.

Doing this can prevent thermosyphoning, however, thermal convection can still occur. Additionally, if bending the pipes isn’t an option for you, you can install a non-return valve. Be aware that doing this can result in increased flow resistance.

2. Flow Restriction

Flow restriction is an issue that can occur with ball heat traps. What happens is that the ball gets stuck inside the heat trap. The ball is prevented from moving when you open the hot water tap, and the flow is restricted. This problem is usually caused by a sloppy installation of the traps.

The Solution

There are two simple solutions. Either loosen the ball with a screwdriver or replace it with a flap.

3. Noise Problem

This problem is again due to the ball. When you use hot water, the pressurized water will stream around the ball inside the heat trap. The ball naturally vibrates which creates a rattle noise. It’s usually a more prominent issue if you have a recirculation pump that creates more pressure.

Fortunately, this may not be an issue if your water heater is placed away from any dwelling areas.

The Solution

Most people recommend that you simply replace the ball with a flap. This will also reduce natural convection by trapping more heat.

Should You Buy One?

Of course, the choice is entirely up to you. Considering that heat traps are inexpensive and capable of saving you some cash, there aren’t many reasons not to.

In saying this, heat traps aren’t without their fair share of problems as we established above. Unless it’s a legal requirement in your state, in the end, it comes down to personal preference.

Tips for Installing Heat Traps

Installing heat traps is very easy and requires only a little plumbing know-how. If you don’t have any experience or want to install a loop heat trap, we recommend consulting a professional. They might be able to bend the present pipes and will avoid any mistakes.

Heat trap nipple kits are easy to find in most hardware stores that provide water heater parts. You can also purchase them through larger manufacturers such as Rheem, A.O. Smith, and Bradford White, among others.

The installation process is pretty straightforward. You’ll need the following:

  • A non-contact circuit tester.
  • Large bucket.
  • Pipe wrench.
  • Heat traps.
  • Teflon tape or another joint compound.
  • A towel.

Here’s a brief explanation on how to install heat traps.

1. Turn the Power Off

Start by locating the right breaker in your breaker box and turning it to the “Off” position. Use the non-contact circuit tester on your heater to check for electricity.

2. Drain the Tank

Drain the tank of approximately 2 gallons of water. You can use the drain valve or relief valve.

3. Remove Nuts From Pipes

Remove the pipe-connecting nuts from the pipe nipples at the top of the unit using a wrench.

4. Apply Teflon Tape

Fasten Teflon tape or another joint compound to the heat traps, then insert them into the hot and cold pipes. If your heat traps are color-coded, then remember — red for hot and blue for cold.

5. Tighten and Finish

Grab the pipe wrench and tighten the nuts.

Do not apply the wrench to the thread, only on the steel body.

Then turn the power back on and you should be ready to go.


Trap That Heat

Water heater heat traps are almost essential to install. They’re available as “nipples” with either a flap or ball, or you can bend the pipes to form a “gooseneck.” Heat traps will prevent any heat from escaping while in standby mode. This increases the efficiency of your hot water tank.

They’re relatively easy to install and inexpensive to buy. Unfortunately, they’re not immune to issues, but luckily these are generally easy to fix.

Have you installed a heat trap? Do you have any tips? We’d like to read your answer below.

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About the Author

Peter Gray

Peter has been a homeowner for 35+ years and has always done his own repair and improvement tasks. As a retired plumber, Peter now spends his time teaching others how they can fix leaks, replace faucets, and make home improvements on a budget.
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2 Reader Comments

  1. Elizabeth R Wilkerson

    Which is better ball or flap type of heat trap? I currently have ball type but it is sticking now. It has been working correctly for 10 years. I see where both are sold but not sure which one would have less trouble in the long run.

    • Sensible Digs

      Hey Elizabeth, thanks for the great comment. A 10-year run is not bad at all!

      We personally think the flap type is the better choice because they are quieter and are also less likely to get stuck and cause a restriction in water flow.

      Hope that helps.

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