'80s or '90s Drainage System diagram?

[johnhh]

Does anyone have a service manual from the 80's or 90's that has a "Drainage System" diagram for a rear shower bath configuration? The drainage diagram shows the 3" pipe routing from the grey and black tanks.

I am wanting to add grey tank capacity to my 78 Tradewind which has the rear shower bath with the black tank mounted above the floor and the 10 gal. grey tank mounted below the floor. Just looking for ideas on how the factory did it before I jump into this project.

Here's mine for a 1978. Is it the same in later models with 30 gal. grey tanks?

Thanks, John H