I agree with Jerry,
That does not look like a central vacuum system to me.
Admittedly, I have never run across a residential one, but in the hospital I work at at night, we have an abandon central vac system that still has all of the piping in place.
Ours is in metal conduit, but the bends are not *teed* like the photo, but large radius sweeps like sanitary drains.
Maybe that's for the in house irrigation system.
