A. O. Smith Water Heater Discharge Pipe Relief Valve Dripping: What to Check and What to Do Next

Use only checks that match the exact appliance or system and its official guide.

1. Check 1

   Make the area safe before inspecting the discharge pipe. Keep hands and people away from any water, identify whether the heater is gas or electric, and use the exact manual to turn off gas or electrical energy and the cold-water supply only when you can do so safely. If you smell gas, see flame or damaged wiring, hear unusual venting, or cannot reach a shutoff safely, leave the area and contact the appropriate emergency or qualified service provider.

   Expected result: The heater and water supply are safely isolated, or hot water, gas, electrical, venting, or access conditions prevent safe isolation.

   Next step: Do not touch the valve or discharge pipe when safe isolation is not possible. Protect people and flooring and arrange qualified plumbing or water-heater service.

   Why this matters

   Why: Isolation limits scalding, gas, electrical, pressure, and water-damage risk. An unsafe or inaccessible shutoff is a stop condition, not a reason to improvise around the relief device.

2. Check 2

   From a safe position, identify the first wet point without touching hot surfaces. Dry only accessible surrounding surfaces with a cloth and observe whether water comes from the discharge-pipe end, the relief-valve threads, the valve-to-tank fitting, the drain pan, or another nearby connection. Do not remove insulation, operate the relief lever, or disconnect the pipe.

   Expected result: Water exits the pipe end, appears around the relief-valve threads, wets the tank-side fitting, collects at the base, or starts at another pipe or connection.

   Next step: Photograph the wet point and keep energy and water isolated. Follow the matching branch below without loosening, capping, plugging, or replacing the relief assembly based on location alone.

   Why this matters

   Why: A pipe-end drip indicates relief-valve discharge; moisture at the threads suggests a connection leak; a wet tank fitting can be a non-repairable welded fitting; water at the base or another pipe may be a different leak or condensation source.

3. Check 3

   Record the timing and amount of a discharge-pipe drip without trying to force a test. Note whether it occurs only while the heater is recovering after hot-water use, at other times with no water use, continuously, or as a large release of hot water. Keep the pipe end unobstructed while observing from a safe distance.

   Expected result: The drip is intermittent during recovery, intermittent while fixtures are closed, constant, or a large amount of hot water is discharged.

   Next step: Do not cap the pipe or adjust the thermostat as a substitute for diagnosis. Keep the heater isolated and arrange qualified service for constant, large, hot, or unexplained discharge.

   Why this matters

   Why: Intermittent recovery drips make thermal expansion or supply pressure more likely; a constant drip can mean a relief valve that is not seating or an unresolved pressure condition; a large hot discharge raises concern about excessive temperature or thermostat malfunction.

4. Check 4

   Inspect the discharge pipe and termination for obvious external blockage, a cap, a valve, crushing, or a change from the installation described in the exact manual. Check that water has a safe path away from people and electrical equipment, but do not alter the pipe, remove the relief valve, or insert anything into it.

   Expected result: The pipe is open and intact, the pipe is capped or blocked, the end is damaged or obstructed, or the discharge path is inaccessible or altered.

   Next step: Do not operate the heater with a blocked, capped, damaged, or incorrectly altered discharge pipe. Keep the heater isolated and arrange qualified plumbing service to restore the safety path and diagnose the valve activation.

   Why this matters

   Why: A blocked or altered discharge path removes the intended relief route and is an immediate safety defect. An intact open pipe does not explain why the valve is discharging; the pressure or temperature cause still needs diagnosis.

5. Check 5

   Check for signs of a pressure or thermal-expansion pattern without measuring or adjusting the system yourself: note whether the drip follows a heating cycle while all fixtures are closed, whether the home has a backflow or check-valve condition, and whether a previously installed expansion-control component is present according to the installation records. Do not connect a gauge to the drain valve or alter a pressure-reducing or expansion device as a first check.

   Expected result: The drip occurs during recovery in a closed plumbing system, supply pressure is suspected to be high, an expansion component is absent or uncertain, or the drip occurs independently of recovery.

   Next step: Have a qualified plumber evaluate system pressure, thermal expansion, and the relief valve together. Do not rely on the relief valve to manage expansion and do not replace it before the underlying condition is assessed.

   Why this matters

   Why: A. O. Smith associates intermittent relief discharge with thermal expansion and pressure conditions, but a symptom pattern cannot establish the required pressure setting or select an expansion component. Drips independent of heating make a seating, valve, temperature, or other plumbing fault more likely.

6. Check 6

   Check the surrounding heater for a separate source before attributing every puddle to the discharge pipe. Inspect only cool, accessible inlet and outlet connections, the drain valve, the tank base, and the pan; also note temporary condensation after a cold refill or startup. Do not remove covers, loosen fittings, or treat a wet tank base as a relief-valve problem.

   Expected result: A nearby connection or drain valve is wet, condensation disappears as the heater warms, the tank base remains wet, or only the discharge-pipe end becomes wet.

   Next step: Keep energy and water off and arrange the appropriate qualified service for any recurring leak or wet base. Do not replace the relief valve to address water that starts elsewhere.

   Why this matters

   Why: Runoff, condensation, a drain-valve leak, or an internal tank leak can resemble relief-pipe discharge. A wet base with dry external fittings is a serious tank clue; an isolated wet pipe end keeps relief-valve activation in scope.

7. Check 7

   After a qualified repair, verify from the exact manual that the discharge path remains open, all fittings are secure, and the tank is full before normal operation is restored. Observe one normal recovery from a safe position and record whether discharge returns; do not reset, lift, or repeatedly cycle the relief valve to reproduce a drip.

   Expected result: The pipe stays dry, intermittent discharge returns, a large hot discharge occurs, the discharge path is blocked, or the tank cannot be confirmed full.

   Next step: Keep the heater isolated and call the qualified plumber back for any returning discharge, hot release, blocked pipe, or uncertain tank fill. Never restore operation by capping the pipe or bypassing the relief device.

   Why this matters

   Why: A dry recovery supports a corrected condition, but returning discharge means the relief, pressure, temperature, expansion, or installation issue remains unresolved. A blocked path or incompletely filled tank creates an immediate safety or equipment risk.