What hot water extraction actually does
Heated solution is delivered into the pile under pressure and immediately recovered through a vacuum slot in the same head. The heat lowers the viscosity of oils so they release from the fibre, the pressure carries solution down to the base of the pile where the soil actually sits, and the recovery slot pulls the loosened material back out. It is the method most carpet manufacturers specify, and for heavily soiled residential carpet it removes substantially more than any alternative.