Close this search box.

Why A Water Heater Leaks From The Overflow Pipe (Explained)

Note: This post may contain affiliate links. This means that at no cost to you, we may receive a small commission for made purchases.

If a hot water tank overflows due to low pressure or excessive heat, the overflow tube has been designed to direct the excess water into another container before leaking onto the ground.

This water then flows through a drain pipe and exits via a downspout.

How To Get Rid Of Water Heater Odor

If the downspout cannot handle the volume of water, it will eventually back up and leak under the cabinet door.

The problem occurs because the drainpipe slopes downward at a steeper angle than the main drainpipe.

When the level inside the tank reaches the point where the water spills over the lip of the tank, some of the water will flow backward into the main drainpipe.

Since the main drain pipe slopes downward at an even steeper angle, it catches the water flowing backward and forces it to travel upward instead of exiting via the downspout. 

This article will discuss why water heaters leak from the overflow pipe and what you can do about it.

What Is A Water Heater?

A water heater is a device that heats water for use in your home.

It’s a vital part of any household because, without it, you would have no way to get warm water when needed.

There are two types of water heaters – electric and gas-fired.

Electric water heaters use electricity to generate heat while gas-fired water heaters burn natural gas to create heat.

How Does A Water Heater Work?

The basic function of a water heater is to heat water. To accomplish this task, it uses either electricity or natural gas.

These fuels are converted into heat by passing them through coils located within the water heater (see also ‘Water Heater Keeps Turning Off (Reasons & Fixes)’) tank.

As the fuel passes through these coils, it releases heat energy which warms the water stored in the tank.

The amount of time it takes for a water heater to heat water depends on how much water is being heated and the type of fuel used. 

For example, if you want to heat 1 gallon of water, it will take approximately 10 minutes to heat with electricity.

However, heating 6 gallons of water will only take 30 seconds using electricity.

Electricity is also more efficient than natural gas because it produces fewer carbon emissions. 

If you live in an area where there is not enough natural gas available, you may be forced to choose between having a gas-fired water heater or buying an electric one.

Either choice has advantages and disadvantages.

Electricity Vs Gas

Electricity is generally considered to be more environmentally friendly than natural gas because it generates fewer greenhouse gasses.

In addition, it is easier to install and maintain than natural gas.

Natural gas is cheaper than electricity but it is harder to install and maintain.

Natural gas requires special equipment such as a regulator and venting system.

You must also ensure that all appliances that use gas are properly vented and connected to the proper piping.

Water Heater Maintenance Tips

To keep your water heater working efficiently, you need to perform regular maintenance checks. Here are some tips:

1) Check the temperature gauge regularly. Make sure it reads at least 120 degrees Fahrenheit.

This will help prevent damage to your water heater.

2) Inspect the thermostat every month. Replace the thermostat if it is damaged or broken.

3) Clean the fins and drain the pan regularly.

4) Keep the air filter clean, ideally, you should change it once a year. 

5) Drain the tank after each use.

6) Do not leave the water heater unattended. Turn off the power supply before leaving the house.

7) Install a pressure relief valve.

8) Be sure to turn off the power supply before performing repairs.

What Is An Overflow Pipe?

An overflow pipe is a small tube that runs from the bottom of the water heater tank to the top.

When the tank fills up, excess water flows out of the overflow pipe instead of overflowing the tank.

The purpose of this pipe is to protect the tank from bursting due to excessive pressure.

Overflow pipes come in different sizes depending on the size of the tank they are designed for.

They can range from 3/16th inch to 1 inch thick. The larger the diameter of the pipe, the higher the pressure rating of the tank.

How Does An Overflow Pipe Work?

When the tank begins filling, the level rises until it reaches the overflow pipe.

At this point, the water in the tank no longer has any place to go except through the overflow pipe.

It then drains back down into the tank.

As long as the water continues to flow through the overflow pipe, the water pressure inside the tank remains low.

If the pipe were blocked, however, the pressure would build up and eventually cause the tank to burst.

The overflow pipe should always be located above the lowest part of the tank so that when the tank overflows, the water will fall rather than shoot straight up.

The best way to avoid problems with the overflow pipe is to make sure it is well maintained. To do this, follow these steps:

1) Remove the cover plate from the front panel of the tank.

2) Use a flashlight to inspect the underside of the tank. Look for cracks or leaks.

3) Perform a visual inspection of the overflow pipe. Note any loose fittings or corrosion.

4) Test the water pressure by turning on the cold faucet. If there is an issue with the overflow pipe, the pressure may drop slightly.

5) Tighten any loose connections.

6) Fill the tank with hot water and check the pressure again.

If you notice any signs of leakage, contact a professional plumber immediately.

What Causes An Overflow Pipe To Leak?

There are many reasons why an overflow pipe could leak. Some common causes include:

1) Improper installation.

2) Corrosion.

3) Faulty fitting.

4) Clogged filters.

5) Damaged valves.

6) Dirty insulation around the pipe.

7) Poor maintenance.

8) A cracked tank.

9) Low water pressure.

10) Too much heat.

What Should You Do If Your Overflow Pipe Is Leaking?

First, shut off the main breaker switch. This will stop all electrical current flowing through your home’s wiring system.

Next, call a professional plumber.

A leaking overflow pipe can quickly lead to serious damage if left untreated.

Even worse, a damaged overflow pipe can result in a flood. So don’t wait! Call a professional today.

How To Fix A Leaking Overflow Pipe

To fix a leaking overflow pipe, first, turn off the power at the circuit breaker box. Then remove the cover plate from the tank.

Next, use a flashlight to look for any cracks or holes in the tank. Check the overflow pipe for any loose connections or corrosion.

Inspect the pipe itself for any defects such as rusting or cracking. Finally, tighten any loose connections.

Once the overflow pipe is fixed, test the water pressure again. If the pressure is still too high, replace the filter.

Causes Of Too Much Pressure In A Water Heater

When the pressure builds up in a water heater, it usually means one thing: The heating element needs replacing.

This is because the heating element is what heats the water in the tank.

As the temperature of the water increases, the amount of electricity used to keep the water warm also rises.

When the heating element burns out, the heating element no longer works properly.

The best way to prevent this problem is to regularly change the heating element.

However, if you have already replaced the heating element once, chances are good that it will need to be replaced again soon.

Another cause of increased pressure in a water heater (see also ‘Instructions On How To Drain A Water Heater Fast And Improve Performance’) is a clogged drain line.

If the drain line becomes blocked, the water cannot drain away from the tank.

Instead, the water sits inside the tank until it backs up into the overflow pipe.

In some cases, the water level in the tank drops below the bottom of the overflow pipe.

This results in a higher than normal pressure reading.

Causes Of Overflow Pipe Corrosion

Causes Of Overflow Pipe Corrosion

Over time, corrosion can weaken the integrity of the overflow pipe. Corrosion weakens the metal pipes that make up the overflow pipe.

Eventually, these weakened pipes can break down completely.

Corroded pipes can also develop leaks over time.

These leaks can eventually allow water to escape from the overflow pipe and back into the tank.

If you suspect that your overflow pipe has been corroded, contact a professional plumber immediately.

Causes Of Clogged Water Heater Filters

Water filters are designed to trap particles like dirt and debris before they enter the tank.

But sometimes, a filter gets clogged with sediment.

Sediment buildup on a water filter causes the filter to become less effective. It may even begin to leak.

Sediment buildup can occur when there is an excessive amount of minerals in the water supply.

For example, hard water contains more minerals than soft water does.

Hard water is found in areas where there is limestone bedrock. Soft water is found in areas with sandstone or shale rock.

Hard water is harder to clean out of a water filter.

So, if you live in an area with hard water (see also ‘Hard Water Vs. Soft Water And Their Impact On Your Health’), you should consider changing your water filter every six months.

How To Test Your Water Filter

There are several ways to check whether or not your water filter is working properly. Here’s how to do it:

1) Turn off your faucet at the kitchen sink. Then, pour about 1 cup of tap water through the filter.

Wait for 5 minutes. If the water runs clear, then the filter is working fine.

2) Pour about 1/2 cup of tap water through your water filter. Wait for 10 seconds.

If the water runs cloudy, then the filter needs cleaning.

3) Use a test strip to check the quality of your water. You can find test strips at most hardware stores.

Simply dip the end of the test strip into the water.

After 30 seconds, compare the color of the strip to the chart provided by the manufacturer.

4) Check the manual that came with your water filter. The instructions should tell you how often to replace your filter.

5) Contact a local plumbing service provider to perform a water filter replacement.

They can remove any sediment build-up and install a new filter.

Leaky Faucets

Leaks in faucets can occur when the rubber washers become worn out.

Leaks can also occur due to faulty installation.

For example, if the faucet is installed with the wrong type of gasket, then the leak could occur.

Faulty plumbing can also cause leaks. For instance, if there is a crack in the pipe, then the water may seep out.

How To Tell If A Water Heater Needs Replacing

If you see any signs of leaks when you open the valve, then you know that the tank needs replacing.

However, if you see any other signs of leaks, then you should not hesitate to contact a professional plumber. These signs include:

-Water coming out of the overflow pipe.

-Fluid on the floor.

-Wet walls and ceilings.

-Sudden increase in the water bill.

-Increased noise levels.

-Decreased hot water flow.

-Low water pressure.

-Leakage in the basement.

-Strange smells.

-Dirty looking water.

-Slow draining water.

-Leaks in the bathroom.

-Rusty pipes.

-Cracked pipes.

-Overflowing toilets.

-Unusual noises.

-Clogging drains.

-Hard water.

Safety Issues With Leaking Overflow Pipes

A leaky overflow pipe can lead to a dangerous situation.

If the leak isn’t repaired immediately, the water could start pouring down the walls and ceiling.

Finally, a leaking overflow pipe can also pose a health risk.

If the water contains bacteria, mold spores, or viruses, they can easily spread throughout your home.

How To Maintain Your Overflow Pipe

To avoid these problems, you must maintain your overflow pipe. Here are some tips to help you do so:

-Change the filter every three months.

-Check the overflow pipe for any cracks or holes.

-Clean the overflow pipe with soap and water.

-Remove debris from around the overflow pipe.


The overflow pipe is one of the most important parts of your water heater (see also our article on element wrenches).

It helps prevent flooding and it keeps your home safe from fire hazards.

However, a leaky overflow pipe can be very dangerous. So, make sure that you regularly inspect this part of your water heater (see also ‘ Water Heater Hissing? Do This Immediately! ‘).

author avatar
Anthony Barnes
Anthony Barnes is the founder of Water Heater Hub and a second-generation plumber by profession. Before developing Water Heater Hub, Anthony Barnes was a full-time plumber, and he has undertaken a wide variety of projects over the decades. As a second-generation plumber, it was easy for Anthony to get used to the technicalities of all from a tender age


On Key

Related Posts

Is Drano Bad for Pipes? The Truth Revealed

Note: This post may contain affiliate links. This means that at no cost to you, we may receive a small commission for made purchases. When it comes to dealing with clogged drains, many homeowners turn