Water Heater Won’t Stop Draining | Quick Fix Guide

Watching a tank pour water can rattle anyone. This guide gives fast actions to stop the stream, then walks through the real causes and reliable fixes. You’ll get clear steps, safe settings, parts that fail, and simple checks you can do today.

Fast Safety Steps Before You Troubleshoot

1) Turn off energy. For electric, flip the breaker. For gas, set the control to OFF or PILOT. 2) Close the cold inlet valve on top of the tank. 3) Let the unit cool for at least 30 minutes; hot water can scald. 4) Keep kids and pets away.

Quick Map Of Where The Water Is Coming From

Find the exact source. Continuous flow usually exits one of two spots: the threaded drain spigot near the base, or the temperature-and-pressure (T&P) relief valve discharge tube along the side. A dry paper towel helps confirm the wet point.

Source	What It Means	What To Do Now
Drain spigot	Loose cap, worn washer, or debris stuck in the seat	Thread on a hose cap to stop a small drip; plan a valve swap
T&P discharge tube	High temperature or pressure, bad thermostat, high house pressure, or failed expansion tank	Lower setpoint to ~120°F, test the valve, check pressure and expansion
Tank seam or shell	Wall leak from corrosion	Shut water off and replace the heater

Why A Water Heater Keeps Draining — Common Triggers

Over-Temperature Or Pressure Opens The T&P

The relief valve opens when water gets too hot or pressure climbs. Many residential devices are stamped 150 psi and ~210°F. If the discharge tube feels very hot and flow arrives in bursts, the relief is doing its job. Turn the thermostat down and watch for a change. If flow continues, suspect a control fault and book service.

U.S. energy guidance points to a target near 120°F for most homes, which saves energy and lowers scald risk. See the Department of Energy’s tip page on 120°F water heater settings. Set the dial, wait for the tank to cool, and recheck the discharge.

Thermal Expansion In A Closed Plumbing System

Homes with a pressure-reducing valve or backflow device can trap heated water. As volume expands, pressure spikes and the relief opens. Look for a small expansion tank on the cold line. If it’s missing, undersized, or water-logged, the relief may run often. A heavy, sloshy sound when tapped points to a failed bladder.

High Street Pressure Or A Bad Regulator

Attach a gauge to a hose bib or the tank drain and read at rest and while fixtures run. Normal domestic pressure sits near 40–80 psi. Readings that stay well above that range call for a regulator adjustment or replacement and a correctly sized expansion tank.

Debris Lodged In The Drain Spigot

Sediment can catch in the drain seat after a flush and leave the valve weeping. Close the spigot, attach a garden hose, open briefly to purge grit, then close again. If it still drips, thread on a hose cap as a short-term stop and schedule a swap to a brass full-port valve.

Old Tank, Heavy Scale, Or Internal Rust

Brown water, rumbling, and flakes at the drain point to heavy scale and a worn anode. Frequent relief discharge and a hot smell near the top can follow. If the shell weeps at a seam, replacement is the only safe path.

Step-By-Step: Stop The Flow, Then Fix The Cause

1) Pinpoint The Discharge Point

Run a dry tissue along the drain spigot and around the relief tube outlet. A hot line points to relief. A cool drip at the spigot points to the drain valve. A wet seam means the tank is done.

2) Stabilize The System

Close the cold inlet. Bleed hot water at a sink to drop pressure. For relief discharge, set the control to the lowest setting and let the tank rest. Many T&P valves reseat once temperature and pressure fall.

3) Check Temperature Setting

Look at the dial and aim near 120°F. If the knob has letters, choose the factory mid mark, then test at a tap with a thermometer later. A high setpoint can drive relief discharge.

4) Evaluate Pressure And Expansion

With a low-cost gauge, check static and while a faucet runs. Numbers above 80 psi need attention. If you have an expansion tank, check the air charge with a tire gauge when the line is cold and at zero pressure. Match the charge to house pressure. Add air with a pump if needed; replace the tank if the Schrader spits water.

5) Service Or Upgrade The Drain Valve

For a valve that won’t seal, thread on a cap now. When the tank is cool and de-energized, connect a hose, open the spigot to clear grit, then close. If it still drips, plan a swap. Many owners upgrade to a brass full-port ball valve, which seals better and speeds future flushes.

6) Test The Relief Valve Only When Cool

Lift the test lever for a second to confirm flow, then let it snap shut. If the lever won’t seat, replace the valve. Route the tube to a safe drain and keep the end visible.

7) Restore Service And Recheck

Open the cold inlet, purge air at a hot faucet until flow is steady, then power the unit. Watch the discharge tube and drain spigot over the next hour. No drips means the fix held.

Safe Settings And Specs Backed By Manufacturers

Relief devices on typical residential tanks carry two stamped numbers: a pressure setting near 150 psi and a temperature trip near 210°F. The device opens to protect the vessel. Never cap or plug the relief tube. Keep a clear air gap at the drain and route the tube where hot water can’t hurt someone. For a typical rating example, see this Watts relief valve spec showing a 150 psi / 210°F setting.

The U.S. energy program recommends a 120°F target for most households to cut scald risk and save energy. That setting also eases stress that can trigger the relief device. Review the DOE guidance on keeping water near 120°F, then match your setpoint.

Parts And Tools You May Need

• Threaded hose cap for a weeping drain spigot
• New T&P valve matched to tank rating
• Brass full-port ball valve and adapter kit for the drain
• Pressure gauge with garden-hose thread
• 2–4 ft of rigid tube or flexible line to route discharge to a drain
• PTFE tape, pipe dope, and a wrench set

When A Constant Discharge Points To Bigger Issues

If the relief tube runs again and again even at a moderate setpoint, you may have a failed control, a runaway element, or scale on a gas sensor. A licensed tech can test sensors, thermostat contacts, elements, and gas safety controls. Water on the burner tray, scorch marks, or a heavy rotten-egg smell call for service right away.

Prevention: Simple Habits That Cut Drain Episodes

Flush Sediment On A Schedule

Once or twice a year, drain a few gallons until clear. In hard-water areas, plan a deeper flush. This keeps the drain seat clean and reduces rumble and heat loss.

Keep The Setpoint Near 120°F

This temp meets typical needs, trims energy use, and reduces stress on relief devices. If you run a dishwasher without a booster, use the unit’s own heater setting instead of raising the tank.

Watch Expansion And Pressure

Test the expansion tank air charge yearly. Log static pressure. If a city pressure-reducing valve was added recently and relief started dripping soon after, expansion control is likely the missing link.

Inspect The Anode And Nipples

Every few years, pull the anode and check thickness. Less than about half an inch means it’s time for a new rod. Dielectric nipples can also corrode and shed debris that lands in the drain seat.

DIY Or Call A Pro?

Handy owners can cap a weeping drain, swap a drain valve, and replace a relief device on a cooled tank. Gas work, control faults, and high-pressure fixes are best left to licensed pros. If the shell leaks, replace the unit. A burst tank can flood a home in minutes.

Costs, Time, And Effort At A Glance

Task	Typical Cost	Time
Thread on hose cap	$5–$10	5 minutes
Replace drain valve with brass ball valve	$25–$60 parts	45–90 minutes
Replace T&P valve	$20–$60 parts	30–60 minutes
Install or replace expansion tank	$60–$150 parts	1–2 hours
Regulator adjustment or replacement	$80–$250 parts	1–2 hours
Full heater replacement	$900–$2,500	Half day