Is my gas water heater vent safe?
October 30, 2015 3:16 PM   Subscribe

Handyman plastered around water heater ceiling vent--should I have him redo it, and if so, what is the preferred method?

The gas water heater in my recently-purchased top-floor condo is vented through the laundry room ceiling. At my home inspection, there was an opening of approximately 2" all around the metal vent pipe, and I seem to remember the inspector saying he'd prefer to see even more space around the pipe. The city also inspected before escrow closed and didn't require any changes.

Yesterday, my handyman showed me that he had plastered around the pipe, so now there is no opening at all. I think his reasoning was that drafts would come in through the opening, and maybe mice. I'm more concerned about a possible fire caused by the pipe touching the plaster.

When I seemed dismayed, he said he'd remove the plaster if I want. Is that necessary? If so, is there a better/safer way to do this (like a metal collar around the pipe)? What do you call that and where do you buy one? Should I have the handyman install it, or call a plumber?

Or is it safe to leave it this way, with no open space around the vent pipe?
posted by elphaba to Home & Garden (5 answers total)
Plaster is rock. It's not like it burns. The clearance issues for flues are between the flue and flammable materials. So the only reason it'd bother me is that you don't have a way to inspect for clearance inside any more.
posted by straw at 3:31 PM on October 30, 2015

So: Sunnyvale CA's guidance on water heaters:
Venting (CPC 510.6.1.1, 510.7.4.1, 510.10)
All vent piping that runs through ceilings, floors, or walls shall be double-wall metal pipe. The vent and the water heater must maintain clearance from combustible materials (such as wall framing or roofing) as required by the manufacturer, which is typically 1" minimum. The vent shall terminate a minimum 1’ above the roof, be installed with flashing through the roof, and terminate in a listed and approved vent cap. Vents shall also terminate a minimum of 3’ above any building opening (door, operable window, etc.) within 3’ of the termination. Venting shall extend in a generally vertical direction with offsets not exceeding 45 degrees, except one 60 degree offset is permitted. Vents may require additional supports depending on the material and design.
was your home inspector talking about clearance to some interior flammable materials?
posted by straw at 3:33 PM on October 30, 2015

It may violate code, yes. I think it depends on wether the pipe is insulated or double-walled... (On preview, what straw said.)
posted by zennie at 3:36 PM on October 30, 2015

Depends entirely on the construction of the vent pipe. Some venting is zero-clearance.
posted by humboldt32 at 3:52 PM on October 30, 2015

Agreed that it depends entirely on the vent pipe in question. Newer systems tend more and more to be zero clearance. Can you post a photo and the model number of your heater?

You definitely should not just have open space around the vent pipe. It should be closed to the outside. There is probably a collar designed for that purpose available for the specific vent system you have, but there are many different permutations.
posted by ssg at 6:31 PM on October 30, 2015

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