On my 2013 KPTS the compartment on the side goes through a small door and I am able to fit a 15ft Rhino Flex hose with fittings on both ends. I am thinking the compartment is around 15 "x8"x8". It took several tries to figure the method to get the hose in but it does fit.
Craig & Terry in Tennessee
2013 Pinnacle 36 KPTS, Voyager Rear View Camera
2012 F350 CC LB King Ranch, 6.7L TD, Ford 25K hitch, TM TPMS, Diesel Site Coolant Filtration System