How to Fix a Leaking Water Heater: Drain Valve, T&P Relief Valve, and Connections (2026)
A water heater leak comes from one of four locations: the drain valve, the T&P relief valve discharge pipe, the inlet/outlet pipe connections, or the tank itself. Three of these are fixable; one means replacement.
Find the leak source before buying anything — the fix and urgency are completely different. Dry the heater exterior and check: (1) Drain valve (bottom of tank): tighten the valve stem or replace the valve. (2) T&P relief valve discharge pipe (side of tank, usually a copper or CPVC pipe running down the side): the T&P valve is discharging — this can indicate dangerous pressure in the tank, address immediately. (3) Inlet/outlet connections (top of tank): tighten or reseal the fittings. (4) Rust or wet spot on the tank body itself: the tank has corroded through — the heater must be replaced. There is no repair for a leaking tank.
Frequently Asked Questions
Is a leaking water heater dangerous?
It depends on the source. A dripping drain valve or a slow connection leak is a nuisance — low urgency. A T&P (temperature and pressure relief) valve that is discharging is a warning sign: the T&P valve opens to prevent tank explosion when pressure or temperature gets too high. If the T&P valve is discharging: check that the cold water supply is not set too hot (above 140°F), and check for a waterlogged expansion tank if your system has one. Do not plug, cap, or disable a T&P valve — it is a safety device. Replace it with a new one if it is leaking when pressure seems normal. A leaking tank body means the tank is corroding and will fail catastrophically — replace the heater before that happens.
How do I fix a leaking drain valve?
The drain valve is the hose-bib style valve at the bottom of the tank. It can leak from two locations: the valve stem (where the knob/handle is) or the valve body seat (where it screws into the tank). Stem leak: try tightening the packing nut (the nut around the valve stem, just inside the handle) clockwise. If that stops the drip: done. Body/seat leak: the valve needs replacement. Turn off the cold water supply to the heater, connect a hose and drain the tank, use a socket wrench to unscrew the old valve, wrap the threads of the new valve in Teflon tape (3-4 wraps), thread in the new valve, refill the tank. Replacement drain valves are $5–$15 and threaded 3/4-inch — universally compatible.
How do I replace a T&P relief valve?
Turn off the water heater (gas: control to PILOT; electric: circuit breaker off). Turn off the cold water supply. Attach a hose to the drain valve and drain 2–3 gallons to reduce pressure. Have a bucket ready. Lift the T&P valve discharge pipe free of the valve (it usually just rests in the valve outlet). Unscrew the T&P valve using a pipe wrench — it threads into the tank side. Wrap the threads of the new valve with Teflon tape (4-5 wraps). Thread in the new valve — it must be the same BTU/pressure rating as the original (ratings are printed on the valve body). Reinstall the discharge pipe. Refill and relight/restore power. T&P valves are $15–$30.
Water is pooling under the water heater but I can't see where it's coming from. What now?
The most common hidden sources: (1) Condensation — on cold days or right after a refill, the cold tank surface condenses moisture from the air. This is normal and temporary — if it stops after the water heats, it's condensation. (2) The discharge pipe from the T&P valve exits near the floor — a drip might appear to be pooling under the heater but is actually coming from the pipe discharge outlet. (3) Slow corrosion at the bottom of the tank — look for rust-colored staining on the tank exterior at the base. Rust staining indicates the tank wall is corroding from inside.
How old is too old for a water heater repair?
Water heaters typically last 8–12 years. Check the manufacture date: it's encoded in the serial number on the rating label (usually the first letter = month A-L for January-December, next two digits = year, or the first 4 digits = YYMM depending on brand). If the heater is over 10 years old and leaking from the tank body: replace it. If under 10 years old and leaking from a valve or connection: the individual repair is worth doing. A 12-year-old heater with a leaking drain valve is still worth fixing (drain valve = $10 + 30 minutes) — that repair buys another year or two if the rest of the heater is sound.
Find the leak source before buying anything — the fix and urgency are completely different. Dry the heater exterior and check: (1) Drain valve (bottom of tank): tighten the valve stem or replace the valve.
Identify the leak location first — a leaking tank cannot be repaired; all other sources can.
What you need
- Paper towels (for diagnosis)
- Replacement drain valve (if drain valve leaks) — $5–$15
- T&P relief valve (if T&P is leaking) — match BTU and pressure rating to original
- Pipe wrench
- Teflon tape
- Garden hose (for draining)
Step 1: Locate the leak
Dry the exterior of the heater completely with paper towels. Watch closely for a minute. Trace the water to its origin:
- Bottom of tank → drain valve
- Side of tank, copper/CPVC pipe running down → T&P valve discharge
- Top of tank, near pipe connections → inlet or outlet fitting
- Tank body surface → rust spot = tank failure
Step 2: Drain valve leak
If the drain valve is leaking from the stem: try tightening the packing nut (the nut around the valve stem) clockwise with a wrench.
If the valve body itself leaks: shut off cold water supply, drain the tank fully via hose, unscrew the old valve, wrap replacement threads in Teflon tape, install new valve. Refill tank.
Step 3: T&P valve replacement
If the T&P discharge pipe is dripping or discharging: turn off the heater and water supply. Drain 2–3 gallons. Remove the discharge pipe from the T&P valve outlet. Use a pipe wrench to unscrew the old T&P valve from the tank. Install the new valve with Teflon tape on the threads. Re-attach discharge pipe. Restore water and power/gas.
Do not operate a water heater with a blocked or missing T&P valve.
Step 4: Inlet/outlet connection leak
Cold and hot water connections at the top of the tank may use dielectric unions, flex connectors, or direct threaded fittings. Tighten threaded connections with a pipe wrench. For flex connector drips: dry and inspect the ferrule at each end — tighten the compression nut. If a fitting is corroded or cracked: replace it.
Step 5: Tank body leak — replacement
No repair exists for a tank that is leaking through its wall. Shut off the heater and water supply immediately (a tank in advanced corrosion can fail rapidly). Drain the tank. Arrange replacement promptly.
Related guides
- How to Replace a Water Heater — full replacement when tank is the source
- How to Drain a Water Heater — annual flush to prevent sediment corrosion
- How to Fix No Hot Water — no heat diagnosis if the leak is accompanied by no hot water
- Locate the leak
Dry the outside of the water heater with a towel. Locate exactly where the water originates: at the drain valve near the bottom; at the T&P relief valve or its discharge pipe on the side; at the inlet/outlet pipe connections at the top; or at the tank body itself (rust streaks or wet seams on the tank shell). Each source has a different repair. Tank body leaks mean full replacement — do not attempt to seal a rusted tank.
- Fix a drain valve leak
The drain valve at the tank bottom leaks from two places: the packing nut or the valve seat. First try: attach a garden hose to the valve, open the valve fully and close it firmly — this flushes sediment that may be holding the valve open. If the valve still drips, tighten the packing nut (the nut behind the handle) a quarter-turn clockwise with a wrench. If the valve body is cracked or the seat no longer closes fully, replace the drain valve: shut off the water supply, drain the tank below the valve, unscrew the old valve (3/4-inch male thread), and thread in a brass replacement valve with PTFE tape.
- Replace the T&P valve
The temperature and pressure relief valve (T&P valve) on the side of the tank opens when pressure or temperature is too high. A dripping T&P means the valve has opened due to high pressure, is stuck partially open, or has failed. First check: confirm water pressure in the house is under 80 PSI. If pressure is fine, the valve has failed. To replace: shut off water supply and gas/power. Attach a hose to the drain valve and drain the tank below the T&P level. Unscrew the discharge pipe. Unscrew the old T&P valve (usually 3/4-inch thread). Wrap new valve threads with PTFE tape. Thread in the new valve, reconnect the discharge pipe (must terminate within 6 inches of the floor or to drain). Never cap or plug the T&P discharge pipe.
- Fix inlet/outlet connection leaks
The water connections at the top of the tank use dielectric unions or flex connectors. A drip here is usually a loose fitting or a failed dielectric nipple. Turn off the water supply. Tighten the union nut hand-tight plus a half-turn with a wrench. If tightening doesn't stop the leak, shut off water and drain the tank, then replace the dielectric nipple — these are brass nipples with a plastic liner that prevent galvanic corrosion between steel tank and copper pipe. Match the thread size (3/4-inch is standard). Use PTFE tape on all threads.
- Tank body leak — replacement
Water seeping from the tank seam, bottom shell, or around a corroded fitting welded to the tank indicates internal corrosion. The tank cannot be repaired. Turn off the gas supply (gas water heater) or the circuit breaker (electric). Shut off the cold water supply. Connect a hose to the drain valve and drain the tank fully. Disconnect the supply and hot water outlet connections. Disconnect the gas line or electrical connections. Remove the old unit and install the replacement following the manufacturer's instructions and local code requirements.
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