So I'm trying to have as much knowledge about my basement drains before calling in a professional.
I have a basement area that has been in the past used as a toilet/shower, with the shower running into the floor drain. When this was done by a previous owner they tore up the floor, put a p-trap at the floor drain, connected the toilet after that and put in a drain for the washer before everything exits the house. Everything works well, no gurgling or bubbling. Washer drains great with no backups, floor drain doesn't give any sign of having any problems when I pour large amounts of water down it at a time.
Here's the thing: I have looked everywhere and I can't find a vent. I know, there has to be a vent for it to be working properly. I have attached a link with pictures of the area. There are no pipes running up or down that would be a vent. One you will see running up (by the back of the toilet) is the kitchen drain coming down, but it's vent is the next floor up and goes out the roof, not coming down at all, not connected at all to the basement drains, though.
Picture link: http://bit.ly/1IzajDu
I want to get work done to get a corner shower in but know that there must be some sort of vent.
Any advice? Thank you!