Plumbing, Water Heaters

Why is Your Water Heater Leaking From Overflow Pipe?

Diagnosing a water heater leaking from overflow pipe can be tricky and indicate a serious problem that needs your immediate attention. Not only does this pose a threat to property from water damage, but it also can put individuals at risk of electric shock or other injuries.

Knowing what to do when you encounter an overflow pipe leaking on hot water heater is important to your safety and prevent property damage.

A water heater temperature & pressure relief valve discharge pipe is sometimes called an overflow pipe.

If your water heater overflow pipe leaks, you likely have an issue with pressure inside the tank or a faulty pressure valve. When the pressure in your water heater gets too high, the pressure relief valve opens and expels water from the overflow pipe. A leaking overflow pipe can indicate that:

  • The temperature setting on your water heater is too high
  • There is an issue inside your tank causing pressure to increase beyond the T&P valves threshold
  • The T&P valve is not “set” properly, allowing the valve to remain partially open
  • The T&P valve is faulty
  • You do not have a thermal expansion tank

We’ll help you understand why your heater is leaking from the overflow pipe and the steps you can take to reduce such incidents. 

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Is a Water Heater Leaking from Overflow Pipe an Emergency?

A water heater leaking from an overflow pipe may not be an emergency. At least not in most cases. However, it can be an emergency if your water heater leaks hot water at a high rate or continuously. 

For starters, it can harm you. Water heaters typically have hot water in them. It might be an emergency if you find your place flooded by an overflow pipe leak. Not only that, but the hot water can also scald you. Hot water can leave you with severe burns even at the recommended setting of 120 degrees. 

In such cases, your best bet would be to call a professional plumbing service. Still, you can attempt it f you have the safety equipment to stop the leak while avoiding injury. 

Water Heater Leaking From Overflow Pipe

Why is My Water Heater Overflow Pipe Leaking?

Every heater has a temperate and pressure relief valve. It has one function, as the name suggests. It relieves pressure and temperature from the heater. 

Most heaters have the pressure set at 150 pounds per square inch and temperature at either 120 degrees or 140 degrees. The T&P valve opens when the water heater exceeds these conditions. 

The overflow pipe is responsible for passing the water when the valve opens. A leak from the overflow pipe means your water heater operates above the set temperature and pressure. It needs immediate attention. 

What Causes an Overflow Pipe Leaking on Hot Water Heater?

One of the leading causes of excess pressure in a water heater is when the temperature is set too high.

Manufacturers set a default temperature of 140 degrees Fahrenheit. Users lower it to 120 degrees Fahrenheit. It’s a comfortable setting for most people, giving you wiggle room to keep it from rising too high to uncontrollable levels. The Department of Energy advises that you lower it to 120 degrees. 

Personal safety is one of the key reasons the DOE recommends such a recommendation. At 140 degrees, there is a looming risk of scalding. Any outlet where the water comes out at such a high temperature is a potential risk. 

Beyond safety, energy saving is a great reason to adjust it to 120 degrees. According to the calculations by the DOE, you lose up to $60 annually in standby heat losses and $400 in demand losses. The bottom line, keep the temperature at 120, and you’ll have fewer leaks. 

Pressure can also come from inbound water pressure. Water systems that feed the cold water inlet sometimes have different pressure settings. The recommended water pressure should be about 80 PSI per code. Some heaters have pressure as high as 100 PSI. 100 PSI is too high and might cause huge damage to the heater, especially if the pressure stays consistent. 

When water comes in pressure as high as 100 PSI, it is subjected to high temperature. Increased temperature increases the pressure, causing it to either drain or start damaging the heater. 

If the water pressure cannot be changed, you should consider getting a pressure-reducing valve. Also, you always need a gauge handy to check the pressure. Put the pressure gauge at the hose bib, and it’ll tell you the operating pressure. 

How Do You Fix an Overflowing Water Heater?

1. Shut Off the Power or Gas

The area below the water heater should not be flooded with water if the overflow is not severe. If there is water in the area, the water heater likely has no water, and you need to shut off the gas and/or electrical supply immediately. 

2. Inspect the Heater for Leaks

Look for any leaks around the valves. If there’s a leak and the heater is off, release the pressure by flipping the T&P valve. However, flip it slowly. Most are susceptible to damage if you flip it too quickly. A leak means you must re-thread the valve with Teflon/plumber tape. 

3. Remove Any Debris From the Valve

Usually, dirt clogs the main seal. Find out if debris blocks the seal by opening and closing the valve a few times. Water should drip from the overflow pipe. Flushing should clear any dirt around the seal. 

Checking the valve’s seal is a vital step in troubleshooting the problem. 

4. Release the Pressure From the Entire System

Open a hot water faucet to remove the pressure from the heater. Since the cold water inlet is closed, it should be a momentary flow. 

Now, open the overflow at the bottom of the heater. Attach a garden hose that directs water out of the house or to your home’s drainage. Leave the overflow open for one minute. 

5. Replace the Overflow Pipe

You may have to cut off the overflow pipe depending on how it was put in. After removing the overflow pipe, remove the old valve and install a new one that’s sediment-free. Reattach the overflow pipe, wrapping Teflon tape along the thread. 

6. Confirm All Your Fittings

Run a final check on the tightness of your valves. Reopen the cold water inlet and check the overflow pipe. If there is any leakage, you should call a plumber. 

7. Close Any Open Taps

Close the open taps that should have released all the air and pressure by now. Let the heater fill with water. Close the cold water inlet. 

8. Power On the Heater

Resume normal heater operations by powering on the heater from the main breaker. Make sure the heater fills with water before you turn on the gas or power. 

What Are the Signs of a Water Heater Going Bad?

Did you know you can prevent any heater mishaps through maintenance? Heaters rarely go out of commission without warning. Look out for these signs to figure out what you need to fix. 

  • Constant leaks – Leaks are a glaring sign that your water heater has structural or mechanical problems. It could be leaking from the valves or the tank. As soon as you notice leaks from multiple places, there is a deeper problem you need to address. Fortunately, most leaks are fixable with proper maintenance. 
  • Less hot water – Are you running out of hot water much faster than before? It could be a sign of extreme sediment buildup. See, when sediment builds up in the water heater for an extended period, it reduces water space. You might even have fine crumbs of sediment from hot water outlets. You need to flush your heater. 
  • Inconsistent water temperature – Inconsistent water temperature may be a problem with tankless water heaters. It means the flow rate from the source is too low, or the heater can’t heat the water fast enough. However, where the heater has a tank, inconsistent water temperature indicates breaking water heating elements or a bad thermostat. 
  • Brown or discolored water – If you notice discolored water or brownish coloring in your water, there are chances your water heater has a bad anode rod inside. Water impurities typically gravitate toward the sacrificial anode rod. If the anode rod is not replaced when it’s deteriorated, the harsh minerals in the water begin to eat away at the tank’s inner steel lining. 
  • Unusual noises – Weird noises signal a myriad of possible problems. You’d have to look deeper to find the main problem. Your water heater could be overwhelmed by mineral deposits clogging valves. It might also mean your water pressure is fluctuating. The worst eventuality would be your water heater breaking from the inside, and you need to replace it. 
  • Inconsistent water pressure from the outflows – Low water pressure is worsened by deteriorating the heater’s inner systems. Sediment builds up fast, continually clogging systems and messing with the pressure mechanism. Check your heater if you are getting low flows despite the constant pressure from the main water supply. It may be about to break down and in need of repairs. 

Water Heater Leaking From Overflow Pipe FAQs

Why is water coming out of my hot water heater overflow pipe?

Several potential causes of water coming out of a hot water heaters overflow pipe include a faulty pressure relief valve, a broken dip tube, or excess sediment build-up at the bottom of the tank.

If the pressure relief valve leaks, it could be worn out or defective. If the dip tube is broken, cold water might enter the tank’s hot water side and force its way out through the overflow pipe.

Lastly, sediment buildup in the hot water heater tank can cause excessive pressure to build up, which could also force water out through the overflow pipe.

How do I stop my hot water from leaking overflow?

To troubleshoot your water heater leaking from the overflow valve, you need to shut the water off to the water heater to identify the source of the leak. The most common cause is a faulty TPR valve, broken dip tube, or sediment buildup inside the tank. You should contact a licensed plumber to help troubleshoot and repair the water heater.

Why is water dripping from my overflow pipe?

There may be several reasons why water is dripping from your overflow pipe. It could be due to the temperature and pressure relief valve not closing fully, allowing water to drip out the overflow pipe. You should call a qualified plumber to repair the water heater.


Having a water heater comes with the additional responsibility of routine checks. Regularly checking the pressure and temperature in your system is the line between a few DIY repairs and costly replacements. The best part is you don’t have to do the dirty work yourself.


Hubert Miles | Licensed Home Inspector, CMI, CPI

Hubert Miles is a licensed home inspector (RBI# 2556) with more than two decades of experience in inspection and construction. Since 2008, he has been serving South Carolina through his company, Patriot Home Inspections LLC. As a Certified Master Inspector, Hubert is dedicated to providing his expertise in home inspections, repairs, maintenance, and DIY projects.