Heating, Air Conditioning, Fridge, HVAC/slab venting for AC/Heat


QUESTION: we have a bathroom that's right off the room for the heat and air unit. on the floor under the sink cabinet is a 6 inch vent pipe coming up out of the slab with a metal cap on it. it does not seem to be a vent as their is no air flow with the cap on. with the cap off - there is tons of air. What is this 'hole'? Can we plug it and put a new bathroom cabinet over it? our house was built in 1973.

ANSWER: This was probably a mistake made during construction.  You can probably cut it off at the level of the slab, bend over the metal, and screw a metal plate to it.  Use silicone, or foam sealer to seal the gaps.  Wear hand protection, or get someone experienced with sheet metal work to do it.  Sheet metal can be dangerous to work with.


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cap on vent hole
cap on vent hole  
QUESTION: I am pretty sure it's not a mistake - its a deliberate 6 inch hole in the duct running from the unit to the nearest room which happens to be a bathroom - the cap on it was purchased and fits exactly over it with a flanged out top  - I have attached a picture.... could it be a release valve, a clean out access???? we don't want to cap it if it needs to be there.

What you have may be a common system for your part of the country, and I just have never seen it before.  It is interesting, and any other pictures you have of the system by sticking a camera into the duct, sketches, or any other visuals would be of interest--but not necessary.

As long as you know it is there, It is OK to plug it--You can always gain access again--although it may be inconvenient or impractical or destructive.  If your house was built in 1973 I would think that you just missed the asbestos pipe era.  Are there any brand names on the pipe/system?


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Mike Reavis


Questions related to "Wet Heat". This is heating your home, office etc. with radiators, panels, and convector apparatus. Steam and water heat. I can answer questions about boilers, piping,and associated parts of these systems. Please do not ask for specific information about how I feel about one boiler, etc. over another--These questions should be directed to a licensed contractor that you know of, or that your neighbors and colleagues look to to provide solutions.


I have 20 plus years experience, which has lead to passing my state master HVAC license.


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