How to Fix a Water Heater Flue Pipe Leak

What You'll Need
Sheet metal screws
Flue pipe
Flue cap
Draft hood
Work gloves
High temperature silicone sealant

You’ll want to fix a water heater flue pipe leak right away because improperly vented gas appliances can cause a fire or release carbon monoxide into your home. Below are some tips on how to handle this issue.

Step 1 – Detect Leakage

Inspect the water heater flue pipe. Gas must continuously run upward toward the chimney entrance to provide proper draft. Check if there are any droplets of water on top or on the bottom of the water heater tank, or inside the combustion chamber. Look to see if the draft hood over the vent hole is centered and if the legs are straight and secured by screws (this may depend on the design of the pipe). Check to see if the draft hood and water heated flue pipe connections are properly secured with sheet metal screws.

Inspect if the flue pipe is functioning properly. To do so, put your hand next to the draft hood on top of your water heater–feel whether or not the air is pulled out to the flue pipe. The pipe is functioning properly if you don’t feel any air being returned. Check pipes for rusting or cracks. The most common areas of corrosion are along the bottom portion, assembly points, and where it’s connected to the wall. Wear work gloves while you’re inspecting the pipe, as it may be very hot.

Step 2 – Repair the Flue Pipe

If the flue assembly isn’t rising in an upward direction toward the chimney, adjust the pipe by installing proper support or hangers. A flue pipe with dripping water could have to do with rainwater entering, so replace the flue cap on the roof. Make sure to center the draft hood over the vent hole properly–straighten it and tighten it up, or replace the screws if needed. If the draft hood is damaged, replace it with a new one of the same size. Return airflow means that there’s a blockage that requires immediate cleaning. If you see water, it can also be due to cracks in the flue pipe that need to be sealed with high temperature silicone sealant. If you have a poorly venting flue pipe, try to clean it out. Otherwise, it may have to do with inadequate airflow if your water heater is in a tightly sealed room. If small holes start appearing on the surface of the flue pipe or if the pipe is visibly corroded, it should be replaced immediately.

Step 3 – Get Local Code Information

Hot water heaters and other flue venting appliances must have vents sized according to local codes and if you have even the slightest doubt about how to correctly install your water heater flue pipe, you should obtain information from the American Gas Association or the National Fire Protection Association.