[twindman]

You should add your truck andMontana year and model number to your signature. Then we can better help you as models are built slightly differently.
Also, maybe you figured it out, there are 3 or more tanks to drain - each with a separate drain handle. The one most people miss and have trouble finding is for the kitchen (in most units). The valve is operated thru a pull handle (metal rod) near or between the driver side wheels. You may have to get on the ground to look under there to find it.

My first time out, I couldn't figure something out and just walked down the rows of campers and found another Montana and asked for help!!