There is a door on each barrel giving access to the water space. Fitting the hoses is a pain, the longer on squashes and goes on. The shorter ones on the tee piece require careful juggling. You can't assemble them to the doors, then fit the assembly as there is a nut and stud behind the pipe (!!!). Before you ask, the 'S' shaped hose on the flywheel end is obsolete and unobtainable
Don't bother trying to unscrew the 'filter', it will be very firmly stuck. It is easier to take the inlet manifold off. It isn't a filter, it's a noise suppressor - actually it' a pepperpot exhaust serving as an air intake
Richard