In the hot water extraction method for cleaning carpets, sometimes incorrectly referred to as steam cleaning, the carpet pile is injected with a water and shampoo solution under pressure so that the soil is suspended in the water which is extracted almost at once by a high suction wet vacuum system.
This method is particularly useful for very dirty carpets because it gets deep-seated dirt. It is also useful for removing excess detergent from successive wet shampooings - and together the two methods can restore a very dirty, flattened carpet. Although hot water extraction machines can be rented, it is best to have this type of cleaning done by a professional cleaner because a certain amount of care is needed not to over-wet the carpet and, thus, distort the pile and backing.