Leaking Water Heater
Updated February 20, 2026
Water around the base demands immediate attention -- floor damage, mold, electrical hazards. Could be loose fittings, a failing T&P valve, a bad drain valve, or a rusted-through tank that needs replacement.
Overview
Not all puddles mean a failed tank. Condensation, a dripping T&P valve, or a loose fitting at the top are all common and repairable. But if the tank itself is leaking from the bottom due to internal corrosion, there is no repair -- replacement only. Find the source before assuming the worst.
Symptoms
- Water pooling around the base
- Dampness or rust stains on the tank exterior, especially near the bottom
- Dripping from the T&P relief valve discharge pipe
- Moisture at the cold inlet or hot outlet connections on top
- Hissing or sizzling from water hitting the burner (gas heaters)
- Musty smell or mold on nearby walls or flooring
Common Causes
- Loose inlet or outlet connections -- thermal expansion and contraction loosens the threaded fittings at the top over time. One of the easiest fixes.
- Corroded tank -- glass lining deteriorates, water contacts bare steel, tank wall rusts through. Not repairable. Replacement only.
- Faulty T&P valve -- old, mineral-encrusted, or responding to genuinely high pressure. Drips or streams from the discharge pipe.
- Deteriorated drain valve -- worn washer, cracked plastic body, or mineral buildup preventing a full seal.
- Condensation -- cold water entering a hot tank or humid environment. Drips down to the floor. Not a defect, more common during heavy use.
What You'll Need
How to Fix It
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Identify the Leak Source
Dry the area. Paper towels at different locations: top near fittings, around the T&P valve, near the drain valve, under the tank. Wait a few hours or overnight. Which area gets wet first tells you the source. Top wet? Fitting. T&P discharge wet? Valve releasing. Bottom only with nothing above? Tank itself.
Tip: Wipe the entire tank dry first. Water from the top runs down the side and pools at the bottom, making it look like a tank leak when it is actually a connection. -
Tighten or Replace Inlet and Outlet Connections
Tighten with a pipe wrench -- quarter turn usually enough. Flexible supply lines? Check rubber washers inside, replace if cracked or compressed. Threaded nipples directly in the tank? Water off, drain a few gallons, unscrew, fresh plumber's tape or pipe dope, reinstall. Use dielectric nipples if copper meets steel.
Warning: Do not overtighten on the tank. Threaded ports are welded to thin steel and can crack. -
Address the T&P Relief Valve
Dripping from the discharge pipe? First check: is the valve responding to real overpressure or is it faulty? Temperature should be 120 degrees or below. Water pressure below 80 PSI (gauge at a hose bib). Both normal and it still drips? Replace the valve. Water and power off, drain below the valve level, pipe wrench off the old one, plumber's tape on the new, install. Discharge pipe reconnected, terminates within 6 inches of the floor.
Warning: Never cap or plug the T&P discharge. Critical safety device. If it is releasing due to genuinely high pressure, install a thermal expansion tank on the cold line instead of disabling the valve. -
Fix or Replace the Drain Valve
Common on tanks with plastic drain valves. Tighten the handle to make sure it is fully closed. Still drips? Garden hose on, open and close a few times to flush debris. Cracked or will not seal? Drain the tank, unscrew old valve, plumber's tape, install new one. Brass upgrade over plastic is worth it.
Tip: Temporary fix: garden hose cap with a washer on the dripping valve. Stops the leak while you plan the replacement. -
Check for Condensation vs. Tank Failure
Ruled out fittings, T&P, and drain valve? Could be condensation or tank failure. Condensation: more likely if the heater is new, recently refilled with cold water, or in a humid basement. Light moisture film that goes away on its own. Steady drip or stream from the tank body near welds or bottom seams? Internal lining has failed, tank is corroding through. No repair.
Warning: A tank leaking from the body can fail catastrophically -- 40-80 gallons at once. Confirm a tank leak? Water supply and power off immediately. Plan replacement. -
Minimize Damage While Awaiting Repair
Waiting for replacement or a plumber? Cold water supply off, gas or electricity off. Open a hot faucet to relieve pressure. Towels or wet/dry vacuum for the water. Heater near finished surfaces? Act fast to prevent flooring and drywall damage.
When to Call a Pro
Call a plumber if the tank is leaking from the body (replacement), if the T&P keeps releasing and you cannot diagnose the pressure issue, if you need a thermal expansion tank, if it is gas-fired and you are not comfortable with gas lines, or if you need urgent replacement. Tank replacement: 2-4 hours professional, includes disposing the old unit.
Prevention Tips
- Flush the tank annually. Removes sediment that accelerates internal corrosion.
- Replace the anode rod every 3-5 years. Protects the tank lining. Single most effective way to extend tank life.
- Test the T&P valve yearly. Lift the lever briefly, confirm water flows, release, confirm it reseats.
- Drip pan under the heater with a drain line to a floor drain. Contains leaks before they cause damage.
- Leak detector or smart sensor near the base. Alert at the first sign of moisture.
- Know the age. Most tanks last 8-12 years. Over 10? Start budgeting for replacement before an emergency.