Ours is plumbed that way as well. I hate it, don't need or want the manufactures help managing tanks, have been doing it for years, with only the pot draining into the black tank, before this motorhome. Some motorhomes, apparently even have the kitchen sink also draining into the black tank, and only the shower going to the grey. Dumb idea. I was told by Thor that my kitchen sink also drained into the black tank. I checked by opening the grey valve only, running hot water into the kitchen sink and got hot water out of the drain, fortunately.
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