Hi, I have an old puisard (sump) (1967) still working ok, not using much since I plan to have a humanore toilet. But still I just want to refresh the whole thing, at the moment the vent is outside and it's just a 1 1/2 inch pipe coming up about 6 feet straight up of the main 4 inchs PVC pipe, I dig the whole thing out and found out why it is sometime stinky inside the bathroom, there is no sewer trap (siphon) P-trap off the 4 inch pipe that goes to the puisard, I look around and something I can see that normal sewer system connected to the city sewer system have all a P-trap but not on regular septic tank. Should I install one? I do have normal P-traps off the bathroom sink, kitchen sink, bathtub and washer, but also there is no vents on any of them, only the outside vent, which seem to me way too small. The toilet is connected directly to the 4 inch sewer pipe. So P-trap on the main 4 inch PVC pipe and vents on part of the system inside. Why you guys recommend?