Double Wall Thermometer Probe Question

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May 12, 2015
Halifax, NS
Anyone have good resources explaining that the probe thermometer (the kind you have to drill through the pipe to install) is perfectly safe and necessary for the double wall pipes? We have double wall stove pipes and I know that the magnetic thermometer will not give us accurate readings. My husband is insistent that it "doesn't seem right" that he has to drill through both walls in the pipe to install the thermometer. He is afraid of "flames" and "smoke" "coming through." I know this sounds ridiculous, as I'm sure the probe basically "plugs" the hole. But I need some pro resources to explain that the probe type is absolutely necessary in our case and that this is what all professionals do.

It's weird that he's being like this, since we installed our wood stove and chimney pipe and everything ourselves. We just followed the directions to a T, and the WETT inspector said we passed with flying colours. My husband didn't question other things and why they had to be the way they were. But something makes him super comfortable about drilling through our stove pipe.


Minister of Fire
Feb 8, 2020
Central MA
Well first of all the chimney draft sucks on the pipe creating negative pressure inside. So if there is any leak, it would be air going into the pipe not flames or smoke coming out. If any smoke does come out, it would indicate a draft problem and you would have already discovered this through the many other gaps and crevices in the very much non-airtight connector pipe.
Secondly, if you drill the correct size hole then the thermometer will cover the hole completely. The one I have is magnetic and sticks against the pipe covering the hole.


Minister of Fire
Feb 8, 2020
Central MA
What kind of "pro resources" do you need to convince him.

Is the probe instructions good enough? It clearly says to drill into the pipe.

Or some of the existing threads on the subject:
We installed an auber flue probe about 2 cords ago... have not seen the slightest scrap of smoke come out it. Like gthomas said, the probe is going to fill the hole and the draft is going to pull air into the pipe through whatever tiny gap is left.


Minister of Fire
Jul 22, 2008
Unity/Bangor, Maine
I'm no probe, but GThomas pretty much nailed it.

1) Natural draft of the chimney will not allow the smoke to escape under normal circumstances.

2) Thickness of the probe and magnet more or less seal off the hole.

Many, many, many folks use these and while it seems counter-intuitive to drill a hole through a perfectly good, solid flue pipe, in general there are no issues.

P.S. Do not attempt this with a water pipe . . .


Staff member
Nov 18, 2005
South Puget Sound, WA
In 17 years of use I have never seen smoke come out behind the probe. It's a small hole and there is a donut-shaped magnet that joins the thermometer body to the stove pipe wall, creating an effective seal. This is a non-issue. Even if the probe was removed, the remaining hole should be under vacuum from the draft. If smoke is coming out of it there is another problem.