What is the Water Heater Overflow Pipe, and Why Is It Leaking?

Last Updated On July 14, 2024

Updated on September 7, 2021



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water heater overflow Is it leaking from the pipe (1)

Did you discover a leaking overflow pipe, also sometimes referred to as the ‘temperature-pressure relief valve drain pipe,’ when you checked your water heater? 

This problem can affect both gas and electric tank-style water heaters, leading to substantial frustration. A leaking water heater can result in water damage or mold. In this situation, it can even result in the tank exploding if the leak developed as a cause of high-pressure levels in the tank and a faulty pressure valve that won’t close in the case of an emergency as designed. 

Luckily, you can take action to resolve the water heater overflow leaking and prevent any further damage to your home and the water heater. 

In this PlumbingNav guide, you will learn:

  • How to identify the overflow pipe
  • Common causes for hot water heater leaking from overflow pipe 
  • How to fix a water heater that leaks or drips from the overflow pipe

What's In This Guide?

      What Is The Water Heater Overflow?

      The water heater overflow consists of the overflow pipe and temperature-pressure valve. The temperature-pressure valve name in itself makes it easy to guess what it does: relieve the temperature and pressure that builds up in the unit. 

      More specifically, the valve will open when water pressure hits 150 psi or the temperature hits 210°F, according to the safety features developed to satisfy building codes

      The overflow pipe sits on the outside of the tank parallel to the water heater. It connects at the very top of the tank, and the temperature-pressure relief valve activates and deactivates it.  The overflow valve provides an outlet to drain the water and pressure in the tank after the temperature-pressure valve becomes activated. 

      The valve opens at those too-high pressure and temperature measurements to prevent excessive pressure buildup in the water heater. In some cases, the pressure buildup can even lead to an explosion if not alleviated. 

      With such an important function, you need to keep the pipe and valve in adequate working condition and know how to use them.

      Can I Open The Pressure Relief Valve Manually In Case Of An Emergency?

      You can manually control the overflow pipe. When you completely open the temperature-pressure valve, you should notice water rushing out of the line. You will need to put the end of the overflow pipe by a drain or in a bucket for the best results. 

      You will also notice a whistling sound. This noise comes from the pressure escaping from the unit. 

      You will need to open the pressure relief valve when you notice your water heater tank struggling to keep its hat on its head (figuratively speaking). Water pressure buildup generally results from a problem with the pressure valve or when the water temperature and pressure get too high. 

      Search for these signs of pressure escalation in your water heater tank:

      • Constantly open temperature-pressure valve
      • Scorching water levels
      • High water pressure levels

      What Is Standard Water Heater Overflow Maintenance? 

      If your temperature-pressure relief valve doesn’t open properly when the unit has high-pressure levels in the tank, it can lead to severe damage to the water heater. In some cases, it can even eventually lead to so much pressure that the unit explodes. That’s why this component deserves your attention. 

      Luckily, keeping up on the overflow pipe doesn’t require too much work. To perform maintenance, you will set a reminder on your calendar to check the component once a year, especially if the water heater has some years under its belt.

      When inspecting the overflow pipe, check that you don’t see a leak, particularly at the connections. Next, ensure that the valve opens and shuts properly. 

      If the pipe or the valve shows signs of a problem, you can likely replace it quite easily, but you need to address the issue before it turns into a bigger problem later. Replace the valve every five years to stay safe.

      did you know The Water Heater Overflow pipe

      Common Causes For A Hot Water Heater Leaking From The Overflow Pipe

      Diagnostics play an essential role when working with the overflow pipe since a wrong diagnosis can lead to more severe repercussions than normal. We will cover the common causes of a hot water heater to leak (or appear to leak) from the overflow pipe. However, double-check that you found the right cause before allowing yourself to get too relaxed. 

      Minor Water Drippage From Drain Valve (Not A Leak – Pressurization)

      Let’s start with a potentially misleading situation. You may approach your water heater and notice water by the drain valve. While the drain did release water, it didn’t leak. 

      When the hot water heater gets pressurized, the valve will automatically open. When this happens, the unit will drain some of the hot water. You can’t release the pressure without also allowing for some drainage since they go hand in hand.

      The water accumulation at the overflow pipe resulted from the tank getting pressurized and the valve opening in response. While not ideal, this is not the same thing as a leak. You may not have experienced this before if the water heater never needed to release pressure on its own. 

      Faulty Valve

      The components on your water heater only last for so long. As you approach the life expectancy of your tank-style water heater, check the valve regularly for deterioration. If you notice a drip coming from the temperature-pressure relief (TPR) valve, recheck it to ensure the device actually has a leak. 

      Both gas and electric storage tank hot water heaters can last up to 15 years. However, many manufacturers now offer highly efficient tank-type water heaters that can last significantly longer. These new, more efficient models tend to be a hybrid electric model or a condensing gas model. 

      If you don’t know the life expectancy of your water heater, check the user manual or look up the serial number on the device. 

      After time, the rust and corrosion in an older tank can get so bad that the pressure valve can’t move, resulting in a damaged temperature-pressure valve. 

      Sediment Buildup

      Water heaters can withstand high temperatures and water pressure levels, but they have a limit. Both scalding water temperatures and high water pressure can result in sediment buildup. 

      The calcium deposits can interfere with the water heater and make it work harder than anticipated, generating hotter water. When water gets hotter than 120°F or has pressure levels higher than 50 psi, the water will expand and generate steam. Mineral accumulation gets left behind, contributing to the cycle of deterioration.

      You may also experience sediment buildup if you have hard water. Hard water refers to water with high concentrations of minerals, calcium, and magnesium in particular.

      How To Fix A Water Heater That Leaks Or Drips From The Overflow Pipe

      If you do identify a leak, you need to fix the problem before the unit breaks down even more. Try these tips to fix a dripping hot water heater. 

      Cut Off Power/ Fuel Source

      First, take the proper precautions before working on your water heater by turning off the power and fuel source to the unit. You will flip the appropriately labeled circuit in the circuit breaker for an electric water heater. If you have a gas water heater, you need to turn the gas knob off. 

      Flush Water Heater 

      Drain the tank and relieve pressure by opening the pressure valve. You will know it opens when the water starts rushing out of the overflow drain. Make a point to be careful, especially if the water seems hotter than normal. 

      While the water drains from the tank, look for signs of sediment in the water. If you still notice sediment in the water at the end of the draining process, activate the cold water supply and drain the tank again and again until it finally runs clear. 

      Replace Temperature-Pressure Valve and Overflow Pipe

      Since they often work together, it can make sense to replace both the temperature-pressure valve and the overflow pipe at the same time when issues arise. 

      Here is how to make those replacements:

      1. Ensure you still have fuel turned off. 
      1. Turn off the cold water supply.
      1. Turn on a hot water faucet to prevent an airlock.
      1. Drain enough so that water levels fall below the pressure valve. Since you will find most temperature-pressure valves on the top of the water heater, you won’t need to drain it too much. 
      1.  Now, you will remove the overflow pipe from the unit. It will have the valve attached to it, and it may require you to cut them apart to fully remove the pipe. 
      1. Once you remove the pipe, you can remove the valve with a wrench. 
      1. Now, wrap the threads of your new valve (with the same pressure and temperature settings) and attach it to the connection on the top of the water heater. 
      1. Wrap the threads to your new overflow pipe and reconnect it to the valve. 
      1. Turn on the cold water supply. 
      1. Close the hot water faucet you opened. 
      1. Verify your new components work properly (no leaks) and you have hot water. 

      Quick Read FAQs for Water Heater Overflow Pipe Issues

      Why is my water heater leaking from the overflow?

      Your water heater leaking from overflow pipe may be due to:

      • Sediment accumulation in the tank
      • Faulty valve/overflow pipe due to age

      Keep in mind that if your hot water heater tank becomes pressurized, it can open up automatically and release water. 

      How do you fix an overflowing water heater?

      1. Flush water heater
      2. Fix components
      3. Replace water heater

      Why is water coming out of my water heater pressure relief valve?

      In rare cases, you may notice water emitting from the temperature-pressure relief valve. In this situation, you probably need a replacement valve since that one went bad. You may also just see water caused by the valve opening when the water heater reaches certain pressure levels.

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      About Plumbing Navigator

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      We write about “all things plumbing,” helping you navigate common questions, repairs, and the best plumbing products on the market.

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