Hi Mark,
Instead of filling the machine with buckets, you can just leave the hose under the tap and allow the Cfr to fill its self. When full it will shut down, allowing you to hoover the carpet while its doing this.
Paul, at 400psi the wand uses 1.25 gallons (4.7 litres) per minute with the Cfr 3 jet wand. I don't know how this compares to your wand? There are so many different wands some with 2/4 jet and all with different nozzle sizes.
Mark