Why is My Water Heater Leaking? How to Diagnose a Leak

When your water heater leaks, the problem is worse than suffering through a cold shower. In addition to being uncomfortable, you’ll face higher utility bills, water damage to your home, and possible system failure.

In this guide, we’ll explore the common causes of a hot water heater leaking and what to do if you discover a leak.

Common Causes of Water Heater Leaks

Why is your water heater leaking? There are many reasons. The problem could be everything from faulty components to pressure issues:

Corrosion and Rust

Over time, minerals in the water cause rust and corrosion inside the tank, weakening the metal and leading to leaks. This is especially true if you’ve never replaced your anode rod — a small metal component that limits corrosion.

Once a tank starts rusting, it usually requires replacement.

Loose or Faulty Drain Valve

The drain valve allows you to flush the tank, but if it’s loose or worn out, it can leak. A simple tightening may resolve the issue. If the valve is leaking because it’s damaged, you should replace it.

Pressure Build-Up

If too much pressure builds inside the tank due to excessive heating or a blocked relief valve, it can force water out through small cracks or seams.

Faulty Temperature and Pressure (T&P) Relief Valve

The T&P relief valve releases excess pressure to prevent the tank from bursting. If this valve is faulty, it may continuously leak even when the pressure is normal. This is a common hot water heater problem that you may be able to fix on your own if you’re handy.

How to Diagnose a Water Heater Leak

Locating the source of a leak helps determine whether you need a repair or a full replacement. Whether your hot water heater is leaking from the bottom or another source, you can follow these steps to diagnose the problem:

1. Check the Inlet and Outlet Pipes

Loose or damaged connections on the hot and cold water pipes can cause dripping. Inspect for moisture and tighten any loose fittings.

2. Inspect the Drain Valve

Ensure the drain valve is fully closed. If water is seeping from it, tightening may help. If it continues to leak, you’ll need to replace it.

3. Examine the Pressure Relief Valve

Look for water dripping from the valve or the discharge pipe. If the leaking persists, it may need cleaning or replacement.

4. Look for Cracks or Rust on the Tank

If water is pooling around the base of the tank and there are signs of rust, the tank itself may be compromised. In this case, you’ll likely need to replace the tank rather than repair it.

What Should I Do If My Water Heater Is Leaking?

If you’ve identified a leak from your heater, it’s important to act fast to prevent water damage. Here are some of the steps you’ll want to take:

Turn Off the Power and Water Supply

Shutting off the hot water heater and cutting the water supply prevents the leak from getting out of control and damaging floors, walls, and other property. Here’s how to do it:

• For electric heaters, switch off the breaker.
• For gas heaters, turn off the gas valve.
• Close the cold water supply valve, usually located near the inlet pipe at the top of the water heater.

Drain the Tank

To prevent water from continuing to seep out of the heater, drain the rest of the tank. Attach a hose to the drain valve and direct the water to your basement floor drain or sink.

Call a Professional Plumber

Once you’ve got the situation under control, it’s time to call in the professionals. A plumber can assess the leak and recommend the best course of action, whether it's a repair or a full replacement.

Can I Still Use My Water Heater If It’s Leaking?

We don’t recommend using your water heater if it’s still leaking. It can put you and your home in danger, not to mention cause further damage.

Risks of Using a Leaking Water Heater

• Electrical hazards: If water seeps into electrical components, it can cause short circuits, fire risks, or electrocution.
• Flooding and water damage: Even minor leaks can escalate quickly, leading to property damage and mold growth.
• Increased repair costs: Continuing to use a leaking unit can lead to more severe damage, requiring expensive repairs or full replacement.
• Structural damage: Persistent leaks can weaken floors and walls, which costs an arm and a leg to fix.

Want to avoid all of these? We recommend performing regular water heater maintenance to keep your unit in top shape.

Is a Leaking Water Heater an Emergency?

Some water leaks may be minor, but others signal a serious issue that requires immediate attention. Here’s when to act fast:

Flooding Risks

A major leak can quickly cause water damage to floors, walls, and nearby belongings. If left unchecked, it may lead to mold growth and foundation damage.

Risk of Tank Explosion

If pressure builds up without proper relief, the tank may rupture, leading to severe damage. A leaking T&P valve is a warning sign of potential pressure issues.

Electrical Hazards

Water leaks near wiring can create fire risks or electrocution dangers. Even small leaks, like the hose bib dripping water, can cause electrical malfunctions over time. 

When to Call a Professional

If you’ve got some handyman knowledge and a bit of elbow grease, you can fix some hot water tank leaks yourself. However, in many cases, the problem is best left to a professional.

Persistent Leaks After Repairs

You’ve tried tightening valves and replacing minor parts, all to no avail. In this case, the issue may be deeper within the system. Professional plumbers have specialized tools to detect hidden leaks.

Rust or Corrosion

Once rust compromises the tank’s integrity, you’ll need an expert to step in. Delaying replacement can lead to catastrophic tank failure.

Water Heater Age

If your unit is over 10-12 years old (the average lifespan of a water heater) and leaks, replacement is likely more cost-effective than doing a ton of small repairs.

No matter what, you shouldn’t ignore leaks. Whether you need repairs or a full replacement, Roto-Rooter’s experienced plumbers can diagnose and fix your water heater issues. Contact Roto-Rooter today for expert service!