I am installing (green) drywall in a room that has a gas water heater vented to the outside through a 6" wall. It has a large metal escutcheon ring around a metal exhaust pipe. The exhaust pipe has an interior exhaust surrounded by a fresh intake jacket. The pipe gets warm. Currently there is (no paper) fiberglass insulation. Do I drywall leaving a large gap around the pipe? Great Stuff expanding foam? I want this job to look good with safety in mind.
I'd just fit around the exhaust reasonably closely and use the escutcheon or another one that's more in fitting the decor (if a room containing the water heater can be said to have "decor" :) ) if that's an issue...
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Aren't there zero clearance flanges for vent pipes? If in doubt, leave space and use a decorative metal flange to cover gap.
Are you sure it gets warm?
Gas water heater vent pipes usually are double walled - the gap acting as a heat barrier.
Nevertheless, sheetrock won't burn (note the "rock" part of the name). The paper covering it might char, but it really won't burn either.
Get from your municipal building permits office the standard specifications for installing a gas heater. You will not need a permit because you are not installing a new fixture, but those two or three pages of the building code will tell you safe clearances for various types of interior or finishing wall.
Followup... I temporarily shut off the heater and removed the pipes. I cut the hole such that a 1" clearance is around the pipe. The escutcheon ring covered the gap and fastens to the drywall. Took a couple hours but finally it's done. Thanks for all the responses.
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