Spilled Lots of Dish Soap into Gray Water Tank - An Issue?

When we volunteer we may sit for 3--4 months I only close the gray tank the day before I dump the black so when we pull out I'll drop a half cup of Dawn down the kitchen and run the hot water till it runs cold. Hit the road. That night when we stop hook up the dumpline and let the crud flow. A couple hundred miles of sloshing realy breaks it up. We try to wipe all plates, bowls and pans before washing but you still wind up with some crud going down the drain.