Hot-water extraction machine

In detail

A hot-water extraction machine sprays a heated detergent solution into a carpet or an upholstered surface under pressure and immediately vacuums it back out, carrying suspended soil with it. It is the method the carpet trade regards as the standard deep clean, and it is often marketed as steam cleaning although it does not produce steam. Its whole advantage over any wet method is the recovery stroke, and its whole risk is that the recovery is incomplete. Solution left in the pile carries residue that attracts soil, so a carpet cleaned badly resoils faster than one never cleaned at all — which is why the trade's rinse guidance is as emphatic as its cleaning guidance. Water left in the backing dries slowly, and slow drying in a carpet is how a musty odour and brown wicking marks appear a day after the job looked finished. Two practical limits for a domestic machine. Its recovery is weaker than a professional truck-mounted unit, so passes should be fewer and drying assisted. And on wool, on natural-fibre rugs, on viscose and on anything with an unknown backing, wetting is itself the risk, and the surface decides before the machine does.

Why

• Hot-water extraction machine is explained by Residue and resoiling

  The extraction half is the point. Detergent left in a carpet attracts soil faster than the carpet did.