The forward grey and black tanks are side-by-side under the pass through storage. The fresh water tank is over the axles, a little towards the aft end. The kitchen grey tank is crosswise at the back of the trailer. Filling the fresh tank will have little affect on pin weight because this tank is over the trailer axles. Weight of the forward black and grey tanks will be shared between the pin and the trailer axles. Weight in the aft tank will unload the pin slightly, but probably less than you are hoping for. For towing stability, you should have 20% to 25% of the trailer weight on the pin. If you contact Grand Design Customer Service with your VIN, they will probably provide the tank layout that you are looking for. The best way to figure out the weight range that you have to work with is to visit a weigh scale with various combinations of tank fill.

Rob

The fresh water tank will be directly above the big white drain valve. Typically it runs cross ways on the trailer somewhere around the axles. I think they try to put the tank over or close to over the rear axle.

howson Cate&Rob TucsonJim One of these moderators may have access to where the tank is located, but again easiest way is to find the drain.

EDIT: I see Rob posted while I was typing.

jhanna4118, I am sorry that you are having pin weight issues. I have been considering the 320MKS as well and have been doing handsprings to figure the expected pin weight. I hope that you don’t mind my asking How much is your pin weight and your max payload. Also, what do you have in the rig that adds to the pin?

David
Future GD owner
Tow Vehicle: 2022 ford F350 Platinum GVWR 11500#