How To Diagnose and Repair a Leaking Water Heater

A leaking water heater can be a homeowner’s nightmare, potentially causing costly water damage. Fortunately, with the right knowledge and tools, you can often diagnose and repair the issue yourself. This guide walks you through identifying the source of the leak and implementing the necessary fixes. In the video, This Old House plumbing and heating expert Richard Trethewey demonstrates how to diagnose and solve a common water heater problem.

Common Causes of Water Heater Leaks

Water heater leaks can stem from several sources, each requiring a different approach to repair. 

Temperature and Pressure Relief Valve

The temperature and pressure (T&P) relief valve is a key safety device that releases excess pressure from the tank. If you notice water leaking from this valve, it could indicate:

• The valve is faulty and needs replacement.
• The water pressure in your home is too high.
• The water temperature is set too high.

Tank Corrosion

Over time, the inside of your water heater tank can corrode, leading to leaks. Signs of tank corrosion include the following:

• Rusty water coming from hot water taps
• Visible rust on the outside of the tank
• Small puddles forming around the base of the heater

Loose Connections

Sometimes, the problem is as simple as loose connections. Check for leaks around inlet and outlet pipes, drain valves, and heating element gaskets for electric water heaters.

Diagnosing the Source of the Water Heater Leak

Before attempting any repairs, identify where the leak is coming from. Follow these steps to diagnose the issue:

1. Inspect the area around the water heater for signs of water.
2. Check the T&P valve for any discharge.
3. Examine all connections and fittings for moisture or drips.
4. Look for signs of corrosion or rust on the tank itself.
5. If the source isn’t immediately apparent, dry the tank and surrounding area, then wait to see where water reappears.

Fixing a Leaking Temperature and Pressure Relief Valve

If you’ve determined that the T&P valve is the culprit, here’s how to address the issue:

1. Test the valve by lifting the lever and allowing it to snap back. If water continues to flow after releasing the lever, you’ll need to replace the valve.
2. Turn off the power to the water heater and the cold water supply.
3. Drain the tank until the water level is below the valve.
4. Unscrew the old valve and replace it with a new one rated for your water heater.
5. Refill the tank and restore power to the heater.

Addressing High Water Pressure

High water pressure can cause the T&P valve to leak. If your home has a pressure-reducing valve, it might be creating an unexpected issue.

1. Check the water pressure coming into your home. Anything above 80 pounds per square inch (psi) is considered high.
2. Ensure the pressure-reducing valve is set correctly, usually between 50 and 60 psi.
3. We suggest installing an expansion tank if you have a pressure-reducing valve or check valve on your main water line.

Installing an Expansion Tank

An expansion tank provides a place for heated water to expand, preventing pressure buildup in your plumbing system. Here’s how to install one:

1. Turn off the water supply and power to the water heater.
2. Drain a few gallons from the tank to lower the water level.
3. Install a tee fitting on the cold water inlet pipe above the water heater.
4. Connect the expansion tank to the tee fitting using the appropriate fittings and pipe.
5. Refill the tank and restore power.

Dealing With Water Heater Tank Corrosion

Unfortunately, if your tank is corroded, the only solution is to replace the entire water heater. Upgrading to a more efficient model can be beneficial. Evaluate these factors when selecting a new water heater:

• Capacity needs based on household size
• Energy efficiency ratings
• Fuel type (gas, electric, or heat pump)
• Available space for installation

Plumbing System Overview

Water heater problems often relate to overall plumbing issues. Here’s a brief overview.

Water Supply Lines

These lines bring fresh water into your home. They’re usually connected to a main water line, which splits off into hot and cold water lines heading toward your faucets and appliances.

Outlet Pipes

Outlet pipes carry hot water from the top of the water heater to your faucets. Leaks often occur at connection points where pipes meet the heater or valves.

Drain Valve

Located at the bottom of the tank, the drain valve allows for tank draining. This is essential for maintenance or replacement. A leaky drain valve generally means a new valve is required.

Electrical and Gas Powered Water Heater Considerations

Before any repair, ensure you understand whether your water heater is electric or gas-powered.

Electric Water Heaters

Electric water heaters rely on heating elements to warm the water. Issues often stem from faulty heating elements, requiring replacement.

Gas Water Heaters

Gas water heaters use a burner to heat the water. Thermocouples or gas valves frequently require adjustment or replacement.

Preventive Water Heater Maintenance

Regular maintenance can help prevent leaks and extend the life of your water heater. Incorporate these tasks into your home maintenance routine:

• Flush the tank annually to remove sediment buildup.
• Check the anode rod every few years and replace if necessary.
• Inspect connections and valves for signs of wear or corrosion.
• Test the T&P valve annually.
• Monitor water pressure and adjust if necessary.

When To Call a Professional Plumber

While many water heater issues can be addressed by a handy homeowner, some situations warrant professional help. Call a water heater technician in these cases:

• You’re inexperienced working with gas or electrical connections.
• The leak is severe or you can’t locate its source.
• You suspect the tank itself is compromised.
• Your water heater is more than 10 years old and may need replacement.
• You’re considering upgrading to a tankless or heat pump water heater.

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