Coachmen Leprechaun fresh water tank

What happened was simple. Some RV's the overflow tube IF when overfilling and water comes out the overflow tube, it starts a SIPHON. When you shut the water OFF, the siphon continues until the water reaches a level where air can then interrupt the process. BUT, this is IF you connected to the Water FILL port. What you did was, you connected to the BLACK TANK FLUSH by mistake. Luckily, the top of the tank is NOT sealed correctly and the overflow ran off the top of the tank. OR, most common, you have "POPPED" the 3 inch toilet down pipe that goes from the toilet to the top of the tank LOOSE and the 3 inch down pipe is NOT sealed to the tank. You can sometimes see this when looking down the toilet with the toilet valve OPEN and no water running. I would flush the tank a few times and then refill the tank with the Black tank flush and monitor the liquid level by watching thru the toilet> have someone outside to turn OFF the water when the water comes UP that 3 inch pipe. If the water does NOT come up that 3 inch pipe the downpipe is not connected to the top of the tank and you will get odors since the tank is not sealed correctly. Doug