Reddit reviews Oatey 39017 SURE-VENT AIR ADM VALVE, 1-1/2-Inch by 2-Inch, White
We found 2 Reddit comments about Oatey 39017 SURE-VENT AIR ADM VALVE, 1-1/2-Inch by 2-Inch, White. Here are the top ones, ranked by their Reddit score.
20 DFU (Drainage Fixture Unit) capacity
You are correct. You could also mount a studor valve (air admittance valve) on it:
https://www.amazon.com/Oatey-39017-Sure-Vent-Admittance-Adapter/dp/B0069KCZO4
Check the secondary after you correct/change the primary, and see if it, too, is leaking cold air.
If this is the case, you can use a air admittance valve under the sink. https://www.amazon.ca/Oatey-39017-Sure-Vent-Admittance-Adapter/dp/B0069KCZO4/ref=asc_df_B0069KCZO4/?tag=googleshopc0c-20&linkCode=df0&hvadid=292930174785&hvpos=1o1&hvnetw=g&hvrand=4194651304515183041&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=1001849&hvtargid=pla-311232934043&psc=1
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They are well within the capability of most DIYers. Put in a Y downstream from the trap, then run pipe to put the valve as close to the top of the undersink space as you can. Not sure why these aren't used more often rather than running stacks.