been living in the camper full time for a couple months. long story but we were selling our house and lived in the camper. so pooping and showering were done in the house. now we are at the campground fulltime. it is a full hookup spot so I just left the sewer drain open. talked with a friend a couple weeks ago and he informed me that was a bad idea. he said drain it every 7 or so days. so I shut the valve. since then I have had the master toilet (yes my camper has 2) clog 3 times. Friday I left it clogged over night with the drain open after the plunger failing to do the trick. my wife tells me over the phone that it was working fine the next day. then Monday night it was clogged again. I tried the plunger again and it doesn't move anything. yesterday, noon, I opened the drain and by 9pm I could use the bathroom, but you could see the top of the water. BTW I tried flushing the black water tank and water goes in and comes out fine. so I believe the clog is between the toilet and tank. any suggestions? thanks in advance.