My basement toilet occasionally overflows. Sometimes the drain pops (water pops back) when I flush, even when there was no solid waste. Some times is flushes just fine. I suspect there is some venting problem. It doesn't appear that the toilet drain has it's own vent. The toilet is about 5 feet from the ejector pump. There is drain pipe that leads off the ejector pump. It appears to be the only vent. Is venting my problem? Is there anything I can do short of ripping apart my tile and concrete floor? The toilet is a conventional gravity fed 3.5 gallon type. Any advice would be greatly appreciated. Thanks.