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Water Heater Leaking 101: The Ultimate Guide to Find the Leak

Water Heater Leaking

You probably weren't expecting to find your water heater leaking. But there it is, sitting in a big puddle of water! The consequences can be anything from mild to catastrophic. A water heater leak may result in only a small amount of water on your floor that is more of nuisance; or it may be a significant flood that can leave a huge dent in your wallet.

Water heater leaks can snowball. What may appear to be a minor, insignificant leak today, can morph into a major flooding disaster tomorrow. But even a small leak is bad news for your floors, sub-floors and walls. You could be looking at extensive damage to your property and hefty repair bills in extreme cases if you do not act fast.

What to Do When Your Water Heater is Leaking

Molds are a Health Hazard

Mold grows in wet and damp areas. If you just found your water heater leaking, and it had been leaking for some time, the surrounding walls and floors are primed for mold growth. 

Aside from the added effort or cost of a mold cleanup, you have to contend with possible mold-related health concerns such as asthma, allergic reactions, or more serious health problems.

Is My Water Heater Leaking?

After noticing water on or around your water heater, your first task is to verify that your water heater is actually leaking. There are a number of things that could be causing the unwanted water. It could be something that is near or around your heater, or it could also be you heater but not actually a leak. 


When humid air comes in contact with a cold surface, droplets of water form in a process called condensation. The water droplets can begin to drip on to the floor and you my suspect the puddle to be a leak. This can happen on the water heater itself, associated pipes, or any nearby appliance. 

Pipe Fittings

Do a quick check on your water heater and related plumbing fittings. If you've ruled out condensation as being the culprit, you may have a leak in your water softener discharge lines, furnace drain lines, or other plumbing.

However, if the pooling of water is directly under or in close proximity to the water heater, then it's a good decision to look closely at your water heater.

First of all, dry the free-standing water on the floor. Then check the water heater and related plumbing fittings for any visible signs of water leakage. If nothing comes up, then the source could be close by. You'll need to be thorough and check the entire space, as the  leak could be coming from an overhead water pipe or other places that are easy to overlook.

Simple Way to Be Certain There's a Leak

If you don't find anything after your comprehensive check, you shouldn’t automatically believe that a leak doesn’t exist. To be certain, simply place some paper towels over the area that you first noticed the water. Check the paper towels periodically, say every few hours, looking for any sign of soaking.

If after a couple of days there is no observable signs of a leak, you are likely in the clear. However, it's a good idea to keep a close eye on the area for awhile just to play it safe. Fifty gallons of water is a big mess to clean up!

Magnifying glass with beaded water

Where's The Leak?

So, you've confirmed that your water heater is in fact leaking. Now we need to identify where the leak is coming from. But first, it's crucial to take a couple safety precautions. 

Safety Precautions

Turn OFF the Power to the Water Heater

  • Electric Water Heaters:
  • Turn OFF the power supply to your heater by flipping the breaker on your household electrical panel.
  • If you're unable to identify the correct breaker switch, because the breakers are not labeled, turn OFF the main breaker.
  • Gas Water Heaters:
  • Turn OFF the power supply to your heater by setting the on/off switch or dial to OFF or PILOT. The switch is located on the gas valve which is attached to the incoming gas line at the bottom of the heater. This will stop the flow of gas to the heater.
  • Selecting PILOT will shut off the gas supply to the burner without extinguishing the pilot light. This is fine for draining the tank or working on water lines, but you may feel more comfortable knowing that absolutely no gas is reaching the water heater.

Turn OFF the Incoming Water to the Water Heater

  • Shut OFF the inflow of cold water entering your water heater.
  • Typically there's a valve located above the water heater, although the design varies. It could be a lever or a dial (gate valve). To shut the valve, you either need to pull the lever down or rotate the dial clockwise.
  • In some situations it may be unsafe to turn off the incoming water or your water heater may not have a cold water shut off valve. If this is the case, you'll need to close the main water shut-off valve to your house.

Be Aware: While shutting off the water supply may slow or even stop the leak, if you haven't identified the source of the leak, you may want to wait until you know where the water is originating.

Always take precautions to avoid coming in contact with hot water. The temperature of heated water in your water heater is often 125 degrees Fahrenheit, but it could be as hot as 190 degrees! Any contact with your skin could lead to scalding and first-degree burns.

Check for Leaks (Where to Look)

​Now it's time to do a proper, comprehensive diagnosis/inspection of your water heater. The fixes will be covered in the next section, but for now, we need to identify the leak.

These are the areas that are most likely to be leaking: 

Cold Water Inlet / Hot Water Outlet

The cold water inlet and hot water outlet pipe connectors and fittings are typically located on the top of the water heater. The cold water inlet is where the cold water enters the tank, and the hot water outlet is where the hot water leaves the tank.

If you discover a leak at either fitting, and its minor, the chances are good that you'll be able to repair problem relatively easily. It may be that the connection is loose and simply needs to be tightened.

Temperature & Pressure Relief Valve (T&P)

The T&P valve is normally on the side of your tank, but is sometimes on the top. This is a safety valve designed to relieve the pressure from within your tank if it reaches an unsafe level.

When the temperature within the tank increases, the pressure also increases. Once the tank pressure reaches it's limit the T&P valve opens to relieve the excess pressure. Water is released thru an attached pipe that runs down the side of the tank and ends near the floor. 

If the valve is the source of the leak, you'll notice moisture at the end of the pipe. The cause could be that there is excessive pressure within the tank and the valve is opening to relieve the pressure (the valve is functioning as intended) or the valve itself is defective. 

If the source of the leak is a defective T&P valve, it is possible to replace the valve. However, if the problem is excessive pressure within your tank, you'll want to identify the cause of the pressure.

Drain Valve

Near the bottom of the tank is a drain valve. As the name suggests, it is a simple gate that allows you to empty the water heater. As part of routine water heater maintenance it will be necessary to empty the tank to remove sediment build-up or perform other repairs.

By default, it should be closed. But sometimes, it may be loose or is defective. If it is loose, re-tightening is all that is required to stop the leak. If it is defective, then your water heater is in need of a new drain valve.

Heating Element

Heating elements are used to heat the water on electric water heaters. Generally, there are 2 elements, an upper and a lower, and they are submersed within the water.

Locate and open the cover plate(s) on the side of the tank and carefully remove the insulation. Inspect the gasket for leaks. Gaskets sometimes become worn or pinched  and water will seep out around the knob of the element. 

If the leak is caused by the heating element, a gasket replacement could be all you need to fix your water heater leaking problem. 

Water Heater Tank

Water heaters are built with an inner steel  tank that holds the water. The tank is wrapped by insulation and then enclosed in an outer cosmetic covering.

Water heater tanks won't last forever. The average life span of a water heater is 8 to 12 years. Flushing the sediment from your tank and replacing the anode rod as needed will help keep your tank healthy, but, time will eventually take its toll.

If you notice a leak from the bottom of your tank, there's a good chance that the tank itself is the cause. You won't be able to see the exact spot, but the water will usually seep from the tank's bottom.

Although, this type of leak is common, there isn't a way to repair the tank. The only option is to purchase a new water heater.

Water with bubbles

I've Identified the Leak - What are My Options?

All water heater leaks require attention, regardless of size. Even the small leaks will eventually become big. The question is, can you repair the leak or do you need to replace the water heater?

If you are a do-it-yourself kind of person you may feel comfortable taking on the project yourself. Many of the repairs are relatively easy and some are as simple as using a pipe wrench to tighten a loose pipe fitting.

If you need to replace your water heater,  you'll need to dispose of your old unit, if you undertake the project yourself. One of the many advantages of hiring a professional is that they clean-up the mess and haul away your old water heater.

If you need to replace your water heater, this may be a good time to consider a tankless system. They are more expensive initially, but they are very energy efficient and can save you money in the long run.

Still, the decision to hire a professional plumber or doing the work yourself really depends on your comfort level with these kinds of projects. One thing to consider is that you will be working with water, and once the tank has filled, it will likely be around 50 gallons. If the job isn't done correctly, 50 gallons of water on your floor can cause a lot of damage.

Sump Pump Installation

Can I Fix My Leaking Water Heater?

You've decided that you're up for the challenge and you're ready to take on the project. Of course. the difficulty and repair depends on the source of the leak.

If you are inexperienced with home plumbing repairs, please do NOT attempt to fix a leaking water heater. It can be difficult, and things can quickly go south if the repairs are not properly completed. We highly recommend hiring a professional plumber.

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Fix for Cold Water Inlet and Hot Water Outlet

If the leak is minor, then you may be able to simply tighten the loose pipe fitting with a pipe wrench. But the problem could also be with the supply hose, in which case you'll need to replace. If the leak is more significant, it's probably best to contact a professional plumber.

How To Replace a Supply Hose

Fix for T&P Relief Valve

As mentioned above, the most common reason a T&P relief valve will leak is:

  • Increased pressure in the tank that forces the valve to open
  • A faulty valve

Here's how to fix these problems:

Fix for Increased Tank Pressure 

To verify that the cause is increased pressure, you'll need to lower the temperature at the thermostat setting. Since temperature and pressure have a direct relationship, reducing the temperature will result in a reduction in pressure.

​After lowering the temperature, turn on the water at the cold water inlet valve and power/gas to your water heater. Monitor the valve for leaks.

If you observe leaks, even after reducing the temperature, then it is likely that you have a faulty valve. However, if you are unsure you may want to consider calling a professional.

Fix for Faulty T&P Valve

If you have a defective valve, the first step is to ensure that it really is defective and not functioning improperly because of debris. 

  • Turn OFF the power and incoming water (see above).
  • Place a bucket under the T&P discharge tube.
  • Open the T&P valve. To do this, pull up the tab on the valve so that its pointing straight out. The discharged water will be very hot.
  • Opening the T&P valve will flush the valve and remove debris. Debris is a common reason why a T&P valve doesn't function properly.

If the leak continues after flushing the T&P valve, you will need to replace the valve. Here's how:

  • Drain the hot water tank. It's not necessary to drain it completely, only so that the water inside the tank is lower than the valve. When you open the T&P valve and water comes out, you'll need to drain more water.
  • Open a hot water faucet. This will allow air to enter the tank.
  • Use a wrench to grab hold of the T&P valve and turn it counter clockwise until the valve is loose.
  • Remove the defective valve.
  • Wrap Teflon tape on the threads of the new valve 4 or 5 times. 
  • Screw the new T&P valve into the water heater. Turn it clockwise for 3 to 4 turns until its firmly locked into place.
  • Turn on the cold water and allow the tank to fill before restoring power to the heater. To confirm that the tank is full, open a hot water faucet. If there's a full stream of water, you can turn on the gas or electricity.
  • Return the discharge tube to the T&P valve to direct any water the valve may discharge towards the floor.
T&P Relief Valve
Rheem SP8346 Temperature and Pressure Relief Valve with 3/4-Inch NPT

How to Replace a T&P Valve

Less Common T&P Leak Issues

Although the above two reasons are the most common causes of a T&P Valve leak, there are a few other issues that could be the culprit.

Rust or Corrosion

Sometimes you may notice a leak coming from the threads of the existing T&P valve. If you see this, follow the instructions above to remove the valve. Then check inside the tank for signs of rust or sorrosion aournd the relief valve area.

If you found signs of rust and corrosion, then you'll need to replace your water heater. Unfortunately, neither flushing the valve or replacing the valve will resolve this leak. 

If you did not  find signs of rust and corrosion, then you may just need to re-wrap the valve threads with Teflon tape and screw it back into place.

External Factors

One thing to note, a leak at the T&P valve may not actually have anything to do with the health of your water heater. Especially, if there are no signs of corrosion inside the valve.

High water pressure in the municipal water system, or from a back flow preventer around the main shutoff or water meter could be likely external causes.

Knowing exactly what the cause is and fixing this type of leak requires the expertise of a licensed plumber.

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Fix for Drain Valve Leakage

There are two main issues that cause the drain valve to leak:

  • Debris is stuck within the drain valve
  • The drain valve is faulty or defective

Here's how to fix these problems:

Fix for Stuck Debris in a Drain Valve

If your drain valve is clogged by debris, your leakage problem should be solved the minute you clear the valve. Here's how to clear a drain valve of debris:

  • Position a bucket directly under the drain valve.
  • Open the drain valve by turning the dial counter clockwise.
  • Opening the valve should allow the tank to drain and flush the valve of debris.

If removing stuck debris doesn’t stop the leakage and you haven’t flushed your water heater tank in a while, then your drain valve may be clogged. Follow the steps in this link to unclog your drain valve.

Drain valves are notorious for clogging with sediment, sometimes to the point where you are unable to drain the tank at all. However, if you were able to flush the sediment from your tank and the leakage is still present, then you'll need to replace the valve.

Fix for a Faulty Drain Valve

If neither flushing not unclogging fixes the drain valve leak, then you'll need to replace your defective valve. Replacing the drain valve is very similar to replacing a T&P valve, except you'll need to drain the entire tank. Follow these steps to replace the drain valve:

  • Attach a garden hose to the drain valve and drain the entire tank.
  • Open a hot water faucet to allow air into the tank.
  • Use a wrench to grab the drain valve and turn it counter clockwise until the valve is loose.
  • Remove the defective valve.
  • Look for signs of rust around the tank opening where the drain valve was. You may want to consider purchasing a new tank if you see excessive rust.
  • Wrap Teflon tape on the threads of the new valve 4 or 5 times.
  • Screw the new drain valve into the water heater. Turn it clockwise for 3 to 4 turns until its firmly locked in place.
  • Turn on the cold water to the water heater and allow the tank to fill before restoring power to the heater. To confirm that the tank is full, check the open hot water faucet. If you have a full stream of water, you can turn on the gas or electricity.
Drain Valve
Rheem SP12112G Brass Drain Valve

How to Replace a Drain Valve

While we recommend replacing a defective drain valve, we realize you may not have the time or the comfort level to perform this task yourself. In which case, you could do a workaround that gets the job done.

Get a brass garden hose end cap. Then screw it onto the threads of the drain valve. Doing this should stop the leak.

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Fix for Water Heater Tank Leakage

A leak from the underside of your hot water tank is the one leak you shouldn’t attempt to fix. This leak is an indication of a serious internal issue.

You could contact a licensed plumber to inspect your heater, but in most cases the only option is to purchase a new water heater. 

Broken Vase

What to Do if You Can't Fix the Leak?

Sometimes, a leak may be a symptom for a more serious issue with your water heater. Therefore, even if you successfully fixed your leak, it's a good idea to keep a close eye on your water heater for awhile.

If you still have a leak after a fix, immediately perform the standard precautionary procedures—switch off the power and turn off the cold water supply,  then call a professional and licensed plumber. Read our extensive article on how to hire a plumber.

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