Water Heater Leaking
Where the water is coming from decides whether this is a fitting you tighten or a tank you replace. Find that out before you call anyone.
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Water under the tank with no wet fitting above it means the tank itself has rusted through, and a rusted tank cannot be repaired — plan the replacement now. Water at a threaded connection, the drain valve, or the relief valve discharge is a different and usually cheaper problem. First: shut the cold inlet, kill the power or set the gas control to off, and then find the highest wet point.
The useful question is not "is it leaking" but "where does the water start". Water runs down and pools at the base, so a puddle on the floor tells you almost nothing on its own. Dry everything, put paper towel down, and look again in an hour at where the first dampness appears.
Where it is leaking from, and what that means
| Where the water starts | Likely cause | What it means |
|---|---|---|
| Underneath, nothing wet above it | The tank has corroded through | Replace. A rusted tank cannot be repaired and gets worse |
| The drain valve at the bottom | Valve not fully seated, worn washer, or sediment holding it open | Often a cheap valve replacement, not a new heater |
| A threaded connection at the top | Inlet or outlet nipple, union or flex connector | Usually tightening or re-making one joint |
| The T&P relief valve discharge pipe | Thermal expansion with nowhere to go, or a failed valve | Check static pressure and whether an expansion tank is fitted |
| Around an element gasket (electric) | Failed element gasket | A repair on a tank under about 10 years old |
| Condensation only when it is running hard | Not a leak | Common on a new or heavily drawn gas tank in a cold room |
The relief valve case, specifically
A T&P relief valve that weeps periodically, usually shortly after the burner or element has run, is the classic symptom of thermal expansion in a closed system. The code position is unambiguous: IPC Section 607.3 requires thermal expansion control on a closed system and states that the relief valve shall not be used to control it. A valve cycled repeatedly by expansion will eventually fail to reseat, and then you have a continuous drip from the one device on the heater you cannot afford to distrust. Expansion tank code requirements has the full text, and expansion tank sizing explains why your static pressure decides the size.
What to do in the next hour
Shut off the water
Close the cold inlet valve above the heater. If that valve will not close, shut the main. You cannot diagnose anything while the tank is being refilled.
Kill the energy
Breaker off on electric; gas control to off on gas. Do not leave a leaking tank heating.
Find the highest wet point
Dry everything, lay paper towel across the top, around the fittings and under the base, and come back in an hour. The first dampness is the source.
Photograph the rating plate
Model, serial and date. The serial number dates the unit, and the age decides whether a repair is worth doing. How long water heaters last covers the arithmetic.
Drain it if the leak is active
Hose from the drain valve to somewhere lower, hot tap open upstairs to break the vacuum. A full 50-gallon tank is over 400 pounds of water you do not want on a floor.
Procedure: Responding to a leaking water heater
Quick picks
Tap any row to read the full assessment below, or go straight to Amazon from the right-hand column. We earn a commission on qualifying purchases at no extra cost to you.
| # | Product | Best for | Price |
|---|---|---|---|
| 1 | Govee WiFi water leak detectorThe cheapest useful leak alarm: a 100 dB siren plus a push and email alert, with one gateway covering up to 20 sensors around the house. | Cheap early warning | Check price on Amazon No live price feed on this site, so we show none. #ad |
| 2 |  Flo by Moen smart water shutoffThe step up from an alarm: it sits on the main, runs a daily micro-leak test sensitive to a single drip per minute, and closes the valve itself when something lets go. | Whole-house automatic shutoff | Check price on Amazon No live price feed on this site, so we show none. #ad |
| 3 | Camco 20841 aluminum pan, 22 inThe 22-inch aluminum pan: the right size under a standard 50-gallon tank, which is itself usually 22 inches in diameter. | 50 gallon tanks | Check price on Amazon No live price feed on this site, so we show none. #ad |
What limits the damage next time
Pick 1 — Cheap early warning
Govee WiFi water leak detector
The cheapest useful leak alarm: a 100 dB siren plus a push and email alert, with one gateway covering up to 20 sensors around the house.
| Alarm | 100 dB, three selectable levels, mutable |
|---|---|
| Alerts | App push and email |
| Capacity | Up to 20 sensors per WiFi gateway |
| Current model | GoveeLife 1s rates a 105 dB alarm and 1,804 ft range |
What is good
- A siren loud enough to hear from another floor
- Email alerts mean you find out while you are away, not when you get back
- One gateway covers the heater, the washing machine and the dishwasher
- Cheap enough to put three around the house
What is not
- It alerts, it does not shut the water off
- Needs working WiFi and a live gateway to send anything
- Battery powered, so it needs checking once a year
Skip it if: Skip it as your only protection if the heater sits above a finished ceiling and you travel. An alert you cannot act on for three days is not protection — that case wants an automatic shutoff valve.
No live price feed on this site, so we show none. #ad
Specifications above from GoveeLife water leak detector 1s product page. We have not tested this unit ourselves.
Pick 2 — Whole-house automatic shutoff
Flo by Moen smart water shutoff
The step up from an alarm: it sits on the main, runs a daily micro-leak test sensitive to a single drip per minute, and closes the valve itself when something lets go.
| Function | Whole-home monitoring with automatic shutoff |
|---|---|
| Detection | Daily micro-leak test; identifies leaks as small as one drop per minute |
| Alerts | App, phone call and email |
| Requirements | 2.4 GHz WiFi and an AC outlet within 10 ft |
| Sizes | 3/4 in, 1 in and 1-1/4 in |
What is good
- It closes the valve, which is the only thing that limits damage when you are away
- A micro-leak test catches the slow failures that rot a subfloor before anyone notices
- Phone-call alerts for people who do not watch app notifications
- Some insurers discount for a monitored automatic shutoff
What is not
- It installs on the main, which usually means a plumber and a shutoff of the whole house
- Needs a power outlet within 10 feet of the main
- Far more expensive than a puck sensor
Skip it if: Skip it if your water main is in a crawlspace with no power. Running a circuit to the main is frequently the larger half of this job, and a pan plus a 100 dB sensor covers the water heater itself for a fraction of the cost.
No live price feed on this site, so we show none. #ad
Specifications above from Moen Flo Smart Water Monitor and Shutoff, 900-006; Home Depot listing, Moen Flo 1 in shutoff. We have not tested this unit ourselves.
Pick 3 — 50 gallon tanks
Camco 20841 aluminum pan, 22 in
The 22-inch aluminum pan: the right size under a standard 50-gallon tank, which is itself usually 22 inches in diameter.
| Inside diameter | 22 in |
|---|---|
| Depth | 2.25 in |
| Material | Aluminum |
| Drain fitting | PVC |
What is good
- Matches the 22-inch diameter of the common 50-gallon tank with room for the fitting
- Aluminum construction
- Standard PVC drain connection
- Fits the alcove a 50-gallon tank already occupies
What is not
- A 22 in pan under a 22 in tank is a tight fit — check the drain boss clears
- 2.25 in depth
- Requires a gravity drain path
Skip it if: Skip it for a heat pump water heater. Those are usually wider than a resistance tank of the same capacity and also produce condensate continuously, which means a larger pan and a committed drain, not a shallow pan.
No live price feed on this site, so we show none. #ad
Specifications above from Pacific Plumbing listing, Camco 20841; HD Supply listing, Camco 22 in ID pan. We have not tested this unit ourselves.
Repair or replace
- Replace if the leak is the tank itself, if the hot water has been rusty, or if the unit is past about 12 years.
- Repair a drain valve, an element gasket, a thermostat or a flex connector on a unit under about ten years old. Those are cheap parts and the tank is fine.
- Investigate rather than replace if the only water is at the relief valve discharge. That is frequently a pressure problem, and a new heater on the same closed system will do exactly the same thing.
- The full decision tree is on replace or repair a water heater.
Stopping the next one being expensive
Every tank leaks eventually; the variable is what is underneath it when it does. A Camco 20841 22-inch aluminium pan under a 50-gallon tank costs very little and turns a ceiling into a mop, provided its PVC drain fitting actually goes to a drain. A Govee WiFi leak detector in that pan tells you at 2am rather than at 7am. A Flo by Moen shutoff closes the main automatically, which is the version that matters if the house is ever empty for a week. And if the heater sits above a finished room, the Rheem Gladiator builds the shutoff into the heater itself and limits a leak to about 20 ounces.
What goes in with it
A water heater is a system, not a box. These are the parts that go in with it, and the ones people discover they need halfway through the job.
- Expansion tank
Required by code on a closed system, which is most homes with a pressure-reducing valve.
- Drain pan
Cheap insurance anywhere the tank sits above something you care about.
- Anode rod
The part that decides when the tank leaks. Replacing it is the highest-value hour of maintenance there is.