In article . com,
DerbyDad03 wrote:

So the real question is: Was my carpet so dirty that even a
professional machine would have taken 2 -3 passes, or are these
machines just not powerful enough to get all the dirt out in one pass?

The major advantage to a professional machine is the massive suction
power. Any old beast will loosen the dirt. But no rental from the
supermarket is going to have any where near the suction of a
truck-mounted machine. No matter how much dirt you suck out, or how many
passes you make, there's still going to be a lot of it that sinks down
into the backing, and the pad, that will not come out. I think that's
what makes carpets so dirty so quickly after they've been cleaned
incompletely.

But keep us posted as you go along, and a few months down the road.