"mark Ransley" wrote in message
...
not meaning to change the subject of oil , but i have an old system that
is fine and it doesnt have vents, why are they needed


Are you sure you don't have a 4 inch pipe going through the roof or up the
side of the house? I've never seen a sewer system, whether on septic or sewer
line, that didn't have a vent pipe. Sewer gasses have to have some way of
escaping or there could be an explosion.

Tom J