Connect a small gas vent to a larger one
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New gas vent system
Install a reducer if you have to increase your vent size by 1-in.
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Close-up of vent pipe reducer
A "reducer" increases your vent diameter by 1-in.
If you find that your new gas water heater has a smaller vent than your existing gas vent, don’t assume that you have to completely replace the venting system. If you can’t find a unit that has
the same size vent opening as
your current water heater (or you just
want a smaller unit), buy one with a
vent opening that’s just 1 in. smaller, then
use a “reducer” to connect to the vent as
shown. Use clamps or sheet metal screws
and aluminum tape to connect the reducer.
Install it on the horizontal part of the
vent, at least 12 in. away from the elbow.
Reducers are available at home centers for
Be sure to check building codes (this
project requires a permit) and manufacturer’s
specifications for any additional