Just had a new gas hot water heater installed today. The guys left and I noticed 3 holes drilled on top far from the draft hood (I saw one of the guys outside doing something to the top of the new heater for awhile before bringing it into the house). It also has some kind of foam seeping out of the top under the hood. Should I be concerned with the extra drilled holes and foam? I contacted the master plumber (he didn't do the work but sent his guys over). He said the insulation is from the factory and said holes are drilled on top to keep the draft vent from moving. My former AO Smith heater, less than 5 yrs old i just replaced, didn't have this foam or extra holes drilled. The master plumber said he was going to call the manufacturer to see what they say. Seems odd he could not answer to this but I feel like i am getting brushed off. Should I be concerned?enter image description hereenter image description hereenter image description here

  • I'm unsure of the holes, but the foam you can just cut it away; it's just excess that seeped out when they filled the shell with insulation. ...in fact, now that I think about it, the holes could be there for the very purpose to allow air to escape during the foam insulation process (again though, I'm unsure)
    – stevieb
    Jul 20, 2022 at 21:38
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    If you feel your contractor isn't being 100% straight with you, you could call the manufacturer directly yourself. They'd be most happy to answer your questions. If they see the pics you've shared with us, they could even confirm that those holes are there for air relief during the foam filling procedure.
    – FreeMan
    Jul 21, 2022 at 17:43

2 Answers 2


The foam is just excess foam insulation that seeped out during the filling process; it can be cut off and removed.

The holes are there to allow air to escape during the foam insulation filling process.

  • ok, my other AO Smith heater they replaced didn't have the holes on top but maybe they are doing that nowadays.
    – LLC
    Jul 20, 2022 at 22:13
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    @LLC It could be that the old tank was insulated with fibreglass batt insulation, which would not require the holes in the first place. All really depends on the shell of the tank and type of insulation.
    – stevieb
    Jul 20, 2022 at 22:15
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    That seeped foam is so close to the vent that I would certainly cut it off just to make sure it didn't overheat and catch on fire or decompose. On a side note, the installers used screws with heads too large for the little straps securing the vent hood, which is why they are crooked. They also didn't use any foil tape on the junctions of the vent pipe, which may not be required but is a sign of good workmanship. No bond between hot and cold and gas pipe is visible in your photo - have someone install one if not already there.
    – Armand
    Jul 21, 2022 at 18:40

That's just extra foam that could be stuffed back into the heater of cut off and removed. The holes are common on many heaters. I've got three just like the ones you've got and three other ones 1" in diameter with plastic plugs in them. Just like the comment from @stevieb, to allow air to escape during the foam filling.

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