Interesting experience, for some time I was sure I could smell an exhaust smell in the house, having a suite in the basement we are close to the appliances that create heat and along with that they also create exhaust gasses. I was positive I could smell it but it was only us on the lower floor no one else, so no one really believed us.
A few “experts” came out but it was difficult because you needed to set up the appointment months in advance and if the smell was not present or strong that day you were SOL. fast forward a couple years and a few visits by both the installer of the new appliances and their brethren they all pretty much told me I was just crazy.
One day in Late October 2021 I was up on the roof cleaning the gutters, winterizing and installing some sewer gas vent covers in an effort to stop access points to prevent rodents getting inside. Basically on a whim I started to examine the vent for the gas hot water tank knowing that it was one of the two appliances in the home that made exhaust gasses.
The first thing I noticed was the louvered cap on the bottom and how fine the slits were I scraped the openings and found them to have some sport of deposits in them but was not sure how much or if it was effecting the flow of air. The second thing I noticed was a very small triangle shaped opening on a seem between the cap and pipe it looked like it went straight thorough, it was not big maybe half the size of a dime so small it was barely noticeable.
I decided to remove the cap and take a look inside see if maybe the louvers were restricted and yes of course there was a bit of curiosity involved I do so enjoy seeing how things tick. So I took it off.
I was surprised at what I found it was unexpected but at the same time it made a lot of sense and left me feeling very validated.
What I found was a combination of carbonized material and what was left of a very small wasps nest. The wasps never really seemed to have built anything substantial and seem to have died in place I can only assume from carbon monoxide and heat.
Set upon the aluminum louvers was a very fine screen designed I surmise to keep such critters out of the chimney, which was bypassed by the small triangular hole I found earlier. While the nest was not very large it was enough to completely block the louvers and eventually stopping the gasses from escaping leading to the death of the architects and I believe the root cause of the exhaust gas smell in the home. The very gasses that I was told did not exist.
The way this particular hot water tank works is its a passive exhaust it uses the heat created to allow the exhaust to rise up and out of the chimney so any resistance creates a real problem. The way the outlet is on the hot water tank is set up is to help create an updraft to allow the gasses to escape but if the gasses cannot escape they simply cool fall back down and empty back into the home, of course its concentrated because the cooled gas mixes with the new hotter gas and as the temperature falls so does the gas.
So while everything seemed tickety boo in the basement none of the repair guys (one of which was the local company who installed both the new furnace and hot water tank) were able to see an issue and not one took the trip up to the roof to check the vent, as if they had they would have seen what I eventually found and seen their error in leaving a gap big enough to allow the wasps in.
Its important to note that the instillation was preformed by an apprentice, so the mistake was an honest one.
After I made the discovery I cleaned it all out, and adjusted the louvers so they were open more, I had discovered during my first attempt at reassembling it that when a person “popped” it back in place the most natural action was an open hand light slap but this action actually bent the louvers closing them up more than normal and exactly how I found them which differed from those in the store and online so I made sure to remedy that when putting it back in place.
I put the cap cleaned and put back to “factory spec” ( lol ) taped the seams back up and in one place for the first time to help prevent any critters from getting back in and causing the same issue again. Yes it is a little Red Green but its also effective and warranted considering that a few little wasps were responsible for some serious health issues and could do it again.
If you have comments or questions please pop them in the provided section Id love to hear your experiences and if this helped you out