Yep! I had my Montana for 3 years and didn't realize there was another turn off valve under the kitchen sink that ran to the ice maker. And it was only a couple months ago I realized there was a drain on that line under the trailer.
I added a drain in the line myself, at the slide a couple years go so I could drain the water from the refrigerator to under the slide. I didn't even see the other low point directly under the kitchen sink valve (3 years and never saw it, right in front of my face). (Duh). Then also learned about the cut off valve under sink. Again, I looked directly at it every time I opened the cabinet door under the sink, and just never saw it (another Duh!).
My added drain in the line between slide out and refrigerator. It was simple to do, and can be removed easily. 1/2 inch PVC pipe worked just fine for a drain.
Cut off line, right beside the refrigerator. Yours may be different based on your floor plan.
Here's the on-off valve under the kitchen sink:
And here's the (Oh Duh) drain valve under the trailer, under the kitchen sink, that drains the ice maker water line. So, now I have 2 drains on that line.
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2019 Montana High Country 375FL
2014 Chevy Silverado Duramax, 6.6L Dually