Water Heater Leaking From the Vent Collar
The Short Answer: Water at the vent collar — the draft-hood ring on top of a gas tank, or the blower adapter on a power-vent — is condensate running down the flue, rain in the termination, a fitting on the head tracking to the ring, or the tank leaking at the center flue. It is not HVAC tape. Indoor drip at a draft hood is a carbon monoxide job until a licensed tech proves otherwise.
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Search Intent & The Real Problem
You are looking at the metal ring on the tank, not the B-vent in the attic. The draft hood sits on a collar over the center flue. Power-vent units use a blower and a gasketed adapter in the same spot. Water shows up there and people search “vent collar leaking” expecting a $20 hood. Sometimes it is leftover flue moisture. Sometimes it is rain. Sometimes a hot-side nipple or T&P on the head runs to the collar and fakes a flue leak. Sometimes the flue tube in the tank has rusted through and tank water is coming up the collector — that vessel is scrap.
Vent pipe joints, laterals, and roof jacks: vent pipe leaking. Drip at an exhaust cap: dripping from the exhaust. Tankless shutdown drip: Rinnai by exhaust. This page is the collar on the heater.
What other guides get wrong
They treat every bead on the collar as harmless condensation, then recommend foil tape. Listed foil is a manufacturer joint seal on some B-vent systems, not a patch over a rusted collector or a 2-inch gap under the hood. They paste tankless condensate advice onto a 40-gallon atmospheric tank. Category I B-vent is not PVC. They replace the T&P because the collar is wet. And they skip the paper-towel test, so an anode weep on the head gets a new draft hood.
Step-by-Step Troubleshooting
Step 1: Name the fluid at the collar
| What you see | Likely source | Next |
|---|---|---|
| Cool drip on the collar only while the burner runs, B-vent above wet | Flue-gas condensate running down | Licensed draft / vent check; not tape |
| Collar wet after a storm, hood otherwise dry in summer | Rain in the termination | Cap / flashing, not a new heater |
| Bead at anode, hot nipple, or T&P, water running to the ring | Head fitting — not the flue | Top leak path, connector |
| Hot water at the collector with every fitting dry, rust at the flue | Tank leaking into the center flue | Replacement. Gas off |
| Power-vent blower adapter wet, gasket torn, inducer rusted | Adapter gasket or condensate in Category III | Licensed. Do not RTV the flue |
| Draft hood wet, yellow flame, soot on the jacket | Combustion spilling | Leave. Utility / fire |
| Steam / white cloud at an indoor hood | Spill, not “steam heat” | White smoke |
- What to look for: Cool vs hot drip. Odor. Soot. Whether the wet spot starts at a water fitting, the hood skirt, or the flue opening in the tank. Dry it. Wait through one burner cycle. See what returns.
- Required tools: Paper towel, flashlight, CO alarm status. No wrench on the vent.
Step 2: Split head-fitting water from flue water
- What to look for: Bradford White, Rheem, and A.O. Smith all park the T&P, anode, and 3/4-inch water connections on the same head as the collar. A dielectric that weeps will paint the collar first. T&P discharge that was never piped dumps onto the hood. Typical relief 150 psi / 210°F. House static over ~80 psi at a hose bib, or a waterlogged expansion tank, will keep that valve dribbling — T&P overflow, expansion tank full.
- Required tools: Hose-bib gauge, tire gauge on the expansion-tank Schrader.
If the fittings are dry and the drip is in the center of the collector, you are past “just a nipple.”
Step 3: Condensate and rain from the vent above
- What to look for: Long horizontal B-vent (code wants rise; laterals collect condensate). Vent diameter bigger than the draft-hood outlet. Dilution air so cold the inner wall sweats. A joint that rotated and unlocked. Bird nest or rust flakes in the cap. Outdoor cap dripping after weather. Same physics as the pipe article, but the water is landing on the tank.
- Required tools: Eyes from the doorway, jacket rating plate (BTU/hr). Manometer work is licensed — typical NG manifold ~3.5 in. w.c., incoming often 5–7 in. w.c.; LP ~10–11 in. w.c. Confirm against that plate.
Condensate in B-vent is still a venting defect. It rusts the inner wall, then the joint leaks flue gas, then the collar rusts. You do not “catch it with a cookie sheet” for a season.
Step 4: Power-vent collar, blower, PVC/PP
- What to look for: Wet gasket under the inducer. Condensate weeping from a Category III seam because the run is long and cold. PVC / polypropylene concentric that is not sloped back to the appliance, so leftover condensate dumps at the adapter instead of the drain. A dead blower you must not fire. Condensing tanks and hybrids make acidic condensate on purpose (often pH ~3–5) — that water belongs in a trap, not the collar. Sister drain: Navien condensate.
- Required tools: Level on the vent (commonly 1/4” per foot back to the appliance). Wet/dry vac on the condensate drain only. Do not fish a hose down the flue.
Do not silicone the blower adapter. Do not run the burner with the inducer off — carbon monoxide.
Step 5: When the collar leak is the tank
- What to look for: Hot potable water at the flue opening with anode, nipples, and T&P dry. Rust flakes in the collector. Water in the burner tray, rust ring at the combustion chamber — the center flue is the tank. Age 8–12+ years, popping, rusty hot water. Do not epoxy the collector. Do not keep firing a flue full of steam.
- Required tools: None. Isolate: appliance cock off, cold inlet off if the closet is flooding — apartment shutoff. Same verdict as a bottom leak that found the fire.
A new draft hood on a tank that is leaking at the flue is a decoration. Replace the heater.
When DIY Ends: Calling a Licensed Pro
It ended the moment the drip was indoor flue, anyone had symptoms, or hot water was coming out of the collector. You may photograph the collar, wipe to name a head fitting, gauge a hose bib, and shut the gas cock. You may not tape the hood, silicone a concentric, or “just run it with a window open.” Combustion, vent replacement, and CO testing are licensed. A $12 roll of foil will not make a rusted flue legal.
Frequently Asked Questions
Q: Why is my water heater leaking from the vent collar? A: Condensate or rain running down the vent, a water fitting on the head tracking to the ring, a failed power-vent gasket, or the tank leaking at the center flue. Cool drip from the pipe is venting. Hot water from the collector is the tank.
Q: Can I seal a leaking vent collar with tape or silicone? A: No. Tape is not a repair for a pulled hood, a rusted collector, or a CO leak. Silicone on a flue is how closets fill with exhaust. Shut it down and hire a licensed plumber or HVAC tech.
Q: Is water at the draft hood a bad tank? A: Not by itself. Condensate and a weeping anode both wet the collar. The tank is bad when hot water returns at the flue with every fitting dry, or the burner tray has a rust ring.