Some traditional shampoos leave behind sticky residues in carpets. If a carpet has been shampooed several times, this residue can cause a considerable volume of foam to build up in the recovery tank, cutting off the vacuum motor before the tank is even a third full with actual liquid. 'NOVARACT' Defoamer is simply poured into the recovery tank in a quantity sufficient to kill the foam according to the tank's capacity. With the foam dispersed, a full volume of liquid can be collected, prolonging the operational time of the machine.