We have other kits for these models. The waste tank is designed to fit on the driver side behind the driver's step between the chassis rail and the sill. It has a capacity of 52 litres. Connections are to the rear.
As described thanks.
Though Im not sure why the waste inlet is so small. Surely it would make sense to match it with sink or shower waste sizes.
As it is i've cut out the waste spigot and fitted a suitable size.