Water Heater Leaking? Here's What to Do (Step-by-Step Guide)

Discovering a puddle of water around your water heater is never a welcome sight. Whether you have a small drip or a steady stream, a leaking water heater demands immediate attention. Left unchecked, even a minor leak can lead to extensive water damage, mold growth, and a complete system failure that leaves you without hot water.

At Karl's Plumbing, Heating & Cooling, we have been helping New York City homeowners and building managers deal with water heater problems since 1935. In this guide, we will walk you through why water heaters leak, how to identify where the leak is coming from, and what steps to take right now to minimize damage.

Why Do Water Heaters Leak?

Water heaters are under constant stress. They heat and store dozens of gallons of water under pressure, day after day, year after year. Over time, this takes a toll on the tank, fittings, and internal components. Here are the most common reasons a water heater starts leaking:

• Age and corrosion. Most tank water heaters last 8 to 12 years. As the tank ages, the interior lining deteriorates and rust begins to eat through the steel. Once corrosion creates a hole in the tank, the only fix is replacement.
• Sediment buildup. Minerals in NYC's water supply settle at the bottom of the tank over time. This sediment layer traps heat against the tank floor, accelerating corrosion and eventually causing cracks and leaks.
• Excessive pressure. When the water pressure or temperature inside the tank gets too high, the system is forced to relieve that pressure somewhere. This often results in leaks from the temperature and pressure (T&P) relief valve or from weakened fittings.
• Faulty components. Drain valves, inlet and outlet connections, and the T&P relief valve can all develop leaks due to wear, loosening, or manufacturer defects.
• Poor installation. Improperly connected fittings, incorrect pipe sizing, or missing expansion tanks can all contribute to premature leaks.

Where Is Your Water Heater Leaking From?

Before you can fix a water heater leak, you need to identify exactly where it is coming from. The location of the leak tells you a lot about the cause and whether a repair is possible.

Leaking From the Top

If water is pooling on top of your water heater or dripping down the sides from above, the most likely culprits are:

• Loose inlet or outlet connections. The cold water inlet and hot water outlet pipes connect at the top of the tank. Over time, these fittings can loosen. Tightening them with a pipe wrench often solves the problem.
• Corroded anode rod port. The anode rod screws into the top of the tank and is designed to attract corrosive elements to protect the tank walls. If the port is corroded, it can leak.
• T&P relief valve. This valve is typically located on the top or upper side of the tank. If it is dripping, it may be releasing excess pressure (which is what it is designed to do) or the valve itself may be faulty.

Leaking From the Bottom

A water heater leaking from the bottom is the most common complaint we hear. Possible causes include:

• Drain valve leak. The drain valve at the base of the tank is used to flush sediment. If it is not fully closed or the valve is worn, it will drip. Try tightening it gently. If it still leaks, the valve may need to be replaced.
• Internal tank failure. This is the most serious scenario. If the leak is coming from the tank itself, it means corrosion has eaten through the steel lining. There is no way to repair a corroded tank. You will need a water heater replacement.
• Condensation. Sometimes what looks like a leak from the bottom is actually condensation. This is common when cold water enters a very hot tank, especially in winter. If the dripping stops when the tank reaches full temperature, condensation is likely the cause.

Leaking From the Pressure Relief Valve

The temperature and pressure (T&P) relief valve is a critical safety device. It opens to release water if the pressure or temperature inside the tank exceeds safe levels. If this valve is leaking:

• The water temperature may be set too high (above 120 degrees Fahrenheit).
• The water pressure coming into your home may be too high.
• The valve itself may be worn and needs replacement.
• A thermal expansion issue may be causing pressure spikes when no water is being used.

Warning: Never cap or plug a T&P relief valve. This valve prevents your water heater from becoming a pressure bomb. If it is discharging frequently, call a Licensed Master Plumber to diagnose the root cause.

Leaking From the Drain Valve

The drain valve at the bottom of the tank is used during maintenance to flush sediment. If it is dripping, first make sure it is fully closed. If the valve is damaged or corroded, a plumber can replace it without replacing the entire water heater.

Step-by-Step: What to Do When Your Water Heater Is Leaking

Follow these steps as soon as you notice a leak:

Step 1: Turn Off the Power

For an electric water heater, go to your circuit breaker panel and flip the breaker that controls the water heater to the off position. For a gas water heater, find the gas shutoff valve on the gas line leading to the unit and turn it to the off position. Do not turn off the gas at the meter unless you suspect a gas leak.

Step 2: Shut Off the Water Supply

Locate the cold water shutoff valve above or near the top of the water heater. Turn it clockwise to close it. If the valve is stuck or broken, you may need to shut off the main water supply to your home. In many NYC apartments and brownstones, the main shutoff is in the basement near the water meter.

Step 3: Identify the Source of the Leak

Dry the area around the water heater with towels and then watch carefully to see where new water appears. Use a flashlight to check the top connections, the T&P valve, the drain valve, and the bottom of the tank. Placing paper towels around different areas can help you pinpoint the exact spot.

Step 4: Contain the Water

Place buckets, towels, or a wet-dry vacuum around the unit to minimize water damage. If the leak is significant, focus on protecting any nearby electrical outlets, appliances, or stored items. In NYC basements, where water heaters are often near electrical panels and furnaces, this step is especially important.

Step 5: Call a Licensed Master Plumber

Once you have contained the leak and turned off the power and water, it is time to call a professional. A Licensed Master Plumber can accurately diagnose the problem and recommend whether a repair or replacement is the best course of action. At Karl's Plumbing, our team responds to emergency plumbing calls 24/7 across all five boroughs, Long Island, and Westchester.

Repair vs. Replace: Making the Right Decision

Not every leak means you need a brand-new water heater. Here is a general guide:

Repair is usually possible when:

• The leak is coming from a fitting, valve, or connection that can be tightened or replaced.
• The T&P valve is faulty but the tank itself is in good condition.
• The drain valve needs replacement.
• The water heater is less than 8 years old and has been well maintained.

Replacement is typically necessary when:

• The tank itself is leaking due to internal corrosion.
• The water heater is more than 10 to 12 years old.
• You have had multiple repairs in the past year.
• The unit is no longer heating water efficiently.
• You are seeing rusty water from the hot side only.

If replacement is the right move, consider upgrading to a high-efficiency model or a tankless water heater that provides endless hot water on demand and takes up far less space, which is a major advantage in NYC apartments and tight mechanical rooms.

Preventing Water Heater Leaks

Regular maintenance can significantly extend the life of your water heater and prevent leaks before they start:

• Flush the tank annually. This removes sediment that causes corrosion and reduces efficiency.
• Inspect the anode rod every 2 to 3 years. Replace it when it is heavily corroded. This sacrificial rod protects the tank lining.
• Check the T&P valve yearly. Lift the lever briefly to make sure it discharges water and snaps back. If it drips afterward, replace it.
• Monitor water pressure. Use a gauge to check your home's water pressure. If it exceeds 80 psi, install a pressure reducing valve.
• Install a drip pan. A drain pan under your water heater catches small leaks before they damage floors, which is especially important for units installed on upper floors or in finished basements.

When to Call a Licensed Master Plumber

While some minor water heater issues can be handled with basic DIY knowledge, you should call a Licensed Master Plumber whenever:

• The tank itself is leaking.
• You smell gas near a gas water heater.
• The T&P valve is repeatedly discharging.
• You cannot identify the source of the leak.
• The water heater needs to be replaced.
• You need a permit for installation (required in NYC for most water heater replacements).

Karl's Plumbing, Heating & Cooling has been serving the New York City area for four generations. Our Licensed Master Plumbers (LMP #921 and LMP #2060) and expert technicians handle everything from minor repairs to complete water heater installations. We also offer professional water leak detection to find hidden leaks before they cause serious damage.

Call us at (800) 721-3200 or (718) 263-8600 for immediate assistance. We are available 24/7 for emergency service across Manhattan, Brooklyn, Queens, the Bronx, Staten Island, Long Island, and Westchester.