Air into cabin

So my brake pressure is low and I have air blowing into my cabin. Both tanks are right around a hundred psi so I'm still driving and obviously I'll stop if they get dangerously low. At this point I cannot hear any air leaks outside the truck or trlr... and I just hit cold weather for the first time yesterday so I'm assuming I probably got some water in my tank.
From what I read on the forms is that I should put alcohol or conditioner into the airline.

This is probably a stupid question but where the heck should I do that at? I got a 2015 Pete 587... I unhook the red line next to the back of the tractor but you have a limited amount of pour before it overflows. Should I put it directly in the air tank underneath the driver's seat? The compressor is kind of hard to get to under the hood.

Again forgive my ignorance driving in cold weather for the first time and never use air breaks before becoming a driver. Any help is appreciated as my carrier just gave me a generic response. I'm pretty sure Tara in the tank because it started exactly when it got to 28 degrees and I never had a problem previous. I know to drain my tanks more often lol

 

062 you got it on the button...its there with tractor or trlr brake...while I'm driving...pretty fun stuff...that's what my service team thought it was the back feed...I checked my chambers no leaks...and can not hear any leaks either... My concern is the compressor blowing up from consistently running