Plumbing, Water Heaters

4 Reasons a Water Heater Leaks (Explained)

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Hubert Miles

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Leaks in water heaters will occur for several reasons. The truth is that your water heater system features many components with the potential to leak. Depending on where the leak is coming from, some leaks may be easier to fix than others. 

Generally, water heaters leak due to loose connections or cracks due to age or corrosion. If your water heater leaks because of a loose connection, you must identify and tighten the component. Leaking due to a crack can be difficult to manage and may require replacing entire parts of your system.

Whether the leak seems minor or significant, it’s important to remember that a leak in a water heater means that something is not functioning as it should in your unit. In this post, we will look at why water heaters leak and where to expect the leaks.

1. Water Heater Leaking from the Top

Most conventional water heaters in the home have a cylindrical shape and are relatively tall. 

The most significant part of the water heater is the tank itself which acts as a reservoir for water. Several pipes are attached to the top part of the cylinder and are often the culprit of leaks coming from the top of the heater.

Leakage on your water heater tank from the top can mean that the water is leaking from any below areas.

A Leak in the Water Intake or Discharge Pipe 

If there is a leak on either of the pipes, it could be because the valve connectors have come loose, and simply tightening them may solve the issue. 

However, corrosion may have eaten at them, and they can no longer tighten to the point where they seal the water in the tank. In such a case, you will need to replace the connector valves.

Connector valves are affordable and available at your local hardware store for about $15. If the leakage is from either pipe due to corrosion, you will need your plumber to replace the pipes for you. 

When it comes to the cold-water inlet connection to the tank, the connection is naturally susceptible to thermal expansion pushes. As a result, the water can find its way out and leak. 

The solution in such a case involves your plumber being meticulous during installation by using Teflon tape and lubricating the area using pipe dope.

Failure to do this, the mismatched metals of steel and copper will corrode each other over time and further make the spot more vulnerable, resulting in a leak. 

Well-experienced plumbers know to give this area the specialized attention it deserves during installation or when repairing a leak on that spot. 

A Leak in the Expansion Tank

The expansion tank can leak due to old age, loose pipe fittings, or the tank itself. The good news is that you can tighten loose pipe fittings with a basic wrench. If the source of the leak is the tank, you need a plumber to replace the expansion tank.

The purpose of a smaller water tank is to accommodate excess hot water when it can no longer fit into the main reservoir. Naturally, when water is heated, it expands.

2. Water Heater Leaking from the Bottom

A water heater leaking from the bottom can be minor with easy and quick fixes, or it can be complex and call for major repairs or a total overhaul of your entire water heating unit.

These bottom leaks often mean one of two things: Either the leak is coming from the drain valve, or the source of the leak is the tank itself. 

If the leak is the drain valve, tightening will do the trick and is often enough to stop the leak. However, if the leak is coming from the tank, a crack or a pinhole may have developed.

There are several reasons why the tank itself can develop leaks; they include

  • Age
  • Sedimentation
  • Deterioration from corrosion 
  • Cracks

Sedimentation in the tank is often the root source of internal tank leaks. 

Water heaters in areas with hard water are particularly prone to experience sedimentation. But that doesn’t mean that locations with soft water are exempt. Sedimentation is the accumulation of calcium and sodium deposits at the base of the tank over time.

When you do not regularly undertake sediment draining from the tank, the tank will rust, crack, or develop holes. 

This deterioration is gradual, happening over a long time, but it eventually leads to a damaged tank. It is best to drain your water heater once in six months to ensure no sediments accumulate at the tank’s base. Your plumber will help drain the tank for you. 

Draining your water heater periodically ensures that your water heater will serve you for the longest time possible while performing at an optimal level. 

Unfortunately, a leaking tank often means the end of the road for your water heater. No band-aid measure will work for this problem. Your plumber will more than likely recommend a new water heater.

3. Water Heater Leaking from the Relief Valve

The temperature and pressure relief valve is abbreviated as (T&P valve). 

When you notice a leak on the T&P valve, you must call your plumber and have it fixed immediately. In the meantime, you can switch off the power and water supply to the water heater as you wait for the plumber to address the issue. The plumber will solve the leak by replacing the T&P valve.

Reasons for a leaking T&P valve include;

  • Thermal expansion
  • Age
  • Corrosion
  • Excessive pressure
  • Not closing the valve properly

This water heater component is located next to the hot water discharge pipe at the top of your unit. 

So, when you see water leaking directly from the T&P valve at the top of your water heater, you should be concerned and inform your plumber promptly. 

Remember that the T&P valve is the most vital safety feature in your water heater. It provides the first line of defense against a tank explosion if internal pressure from hot water gets too high. 

So if it is leaking, it may fail when most needed leading to a blast.

4. Water Heater Leaking Due to Corrosive Elements

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The anode rod is also referred to as a sacrificial rod. Unfortunately, there are many corrosive agents in the water that find their way into the water heater. The elements have a corrosive effect that impacts the health of the tank.

Failure to replace it will mean that the corrosion will eat its way up to the top. 

At that point, the water heater leaks begin to occur through the space previously occupied by the anode rod. The solution is straightforward for this problem. 

Replacement of the anode rod will stop the leakage from that spot.

Ordinarily, these corrosive elements such as sodium and calcium would eat at your tank. But instead, their attention is diverted to the anode rod, and they erode it, hence the sacrificial rod.

The anode rod runs inside your water heater, but the port is visible on the top of your water tank. Because the anode rod will rust with time, it will need replacement once it starts eroding. 

What Can You Do to Prevent Leakages from Your Water Heater?

Given that water heaters don’t come cheap, and you want to enjoy the comfort of the service they provide for the long haul, here are tips on preventing leaks;

  1. Drain and clean your water heater once in six months
  2. Occasionally inspect and tighten loose components
  3. Have periodic scheduled inspections for your water heater by a professional plumber 
  4. In case of any leakages, inform your plumber promptly

The other alternative is investing in a self-cleaning water heater.

These units come with a self-cleaning mechanism that automatically flushes out the troublesome elements that cause corrosion and deterioration of the tank.

In a self-cleaning water tank, the dip tube is curved instead of being straight. The dip tube has an accessory at the bottom that stirs up the water as it heats up. By stirring up the water, the sediment cannot settle to the bottom of the tank.

The stirred-up water is sent to the faucet removing it from the tank. 

A self-cleaning water heater has less sediment build-up, which reduces the chances of corrosion that causes cracks and pinholes in the unit.

You can schedule a manual flush of the self-cleaning water heater every three months. These units can have a lifespan of up to 15 years. 


Water heaters have a lifespan of about 12 years, depending on the manufacturer. However, for your water heater to serve you well and go the distance, you need to be keen on preventative maintenance. 

An ounce of prevention is certainly better than a pound of cure in the case of water heaters. 

And with regular maintenance, it is easier to catch potential leaks and other problems before they compromise the functionality of your water heater. 


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Hubert Miles

I've been conducting professional home inspections since 2002. I'm a licensed Home Inspector, Certified Professional Inspector (CPI), Certified Master Inspector (CMI), and FHA 203k Consultant. I started to help people better understand the home inspection process and answer questions about homeownership and home maintenance.
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