While a friend was visiting from the east coast, he was complaining about the smell coming up through the toilet in his 5th Wheel. As campers ourselves, his complaint was fully understood. After questioning how he was keeping his holding tank. He explained that when he first got his camper, nobody told him not to leave the waste gate valve open while using full hookups at a campground. He was relieved to hear that he was not the only person who was not properly instructed on hookups.