How is the water being carried in as humidty? I thought you were feeding it under positive pressure air that was <10%RH. Or, do you mean the water in the humidity that re-encroaches when you have it switched off at night?
On the larger topic of recommended storage humidity, I find the Bambulab wiki advice seemingly contradictory:
On the one hand it says storing filament at an RH below 20% will keep it dry for “an extended period.” Well, ok, let’s say it’s 19.99999%. But then immediately afterward it says that if it’s kept in 20% RH, it will only remain dry for only approximately 2 to 7 days. What? 2 to 7 days doesn’t sound like much of an “extended period” to me. What if you want to keep it dry for a lot longer than that, say a year or longer? How low should the storage RH be to accomplish that? Or is that very question a non sequitur? If it’s even possible to get solid guidance on that, I sure wish it were more widely known. It’s partly for reasons such as this that I lean toward overkill and hopefully driving the storage RH as close to 0% as I can. Or perhaps a more solid target would be a storage dewpoint of -40C or lower, purely for lack of any other credible reference number and because it seems like it would be a nice, safe overkill number. Speaking only for myself, if I could get to that number and maintain it during filament storage, I’d feel comfortable calling it mission accomplished. Monitor it, of course, but comfortably done until it rises to something north of that. Still TBD as to what the trigger threshold should be to invoke another drying cycle. I don’t know how long it might take to figure that out, so I’d rather solve that on the back-end rather than do nothing at all and not even start drying filaments until I figure it out. I have filaments that are getting older, so I’d rather dry them to a conservative number sometime soon and store them at that number and then figure out an appropriate edge trigger afterward.