Hot water extraction

The Hot Water Extraction (HWE) method, is a method used in chemistry for extraction and for "steam cleaning" (e.g. carpets. as listed by the IICRC to be the primary method for cleaning carpets. Residential, and Commercial). The pressurised hot water extraction (PHWE) process uses a combination of high water pressure for agitation, and hot water to increase reaction rate.

"Steam Cleaning"
Though commonly called "Steam Cleaning", no actual steam is involved in the HWE cleaning process, apart from steam that may escape incidentally from hot water. When the cleaning solution comes in contact with the carpet/rug, it is anywhere between 120-250 degrees Fahrenheit, according to the heat available from the cleaning unit. For instance, in a modern truck-mounted carpet cleaning machine, water can be heated to 300+ degrees (F), but after passing through high pressure steel braided hose and several manifolds, the water loses much of its heat.

The typical cleaning method involves a preconditioning of the soiled surface with an alkaline( 7 or above on the PH Scale) agent, followed by light agitation with a grooming brush and appropriate dwell time. Next, the surface is passed over several times with a cleaning tool (either manual or automatic) to thoroughly rinse out the preconditioner and lower the pH ( 7 or lower on the PH scale, usually an acetic acid ) of the fibres to a neutral state. Finally, the surface is dried sufficiently to avoid any possibility of saturation. Inexperienced carpet cleaning companies sometimes over-wet carpeting, which can lead to mold and recurring stains.