Do you have any guess how much water the dehumidifier might generate?? I would be concerned about possibly filling your Gray Tank, because I wouldn't want to leave them open because of possible visitors from the sewer line.
I know lots of folks in our park here in Sebring, FL that just use buckets of Damp Rid and don't have an issue or use a HumidStat hooked up to their A/C.
Michelle & Ann
2018 Chevy 3500HD Crew Cab High Country DRW, D/A, 2016 RW39MB, Dual ACs, Auto Level, Auto Sat Dish, Stack W/D, King Sleep #, 17.5" Sailuns w/Disc, MORryde IS & Pin, Comfort Ride Hitch, 5.5 Onan, Res Fridge & Induction Cook Top