Besides liquids, are there some materials that my central cleaning system cannot vacuum?

Yes. We strongly recommend against vacuuming abrasive materials such as cement, plaster and gyproc dust. This fine dust could work its way into the motor, causing considerable damage. Should you do so inadvertently, immediately clean the filters and, as a precautionary measure, contact your authorized service center to determine the extent of the damage to the unit. Remember that in order for your warranty to remain valid, maintenance of the motor and repairs to the unit itself must be carried out by an authorized service center, using original Cyclo Vac or Trovac parts.