Every 12 to 18 months. The Carpet and Rug Institute recommends cleaning at that interval, and most major carpet manufacturers require documented professional hot water extraction on the same schedule to keep the wear and stain warranties valid – so keep your invoices.
Local conditions push most Willamette Valley homes toward the shorter end of that window. The valley averages roughly 40 to 50 inches of rain a year, concentrated from October through May, which means six-plus months of moisture and grit tracked in on shoes. Add the region’s heavy grass pollen season in late spring and early summer, and carpet in a Salem or Springfield home takes on more soil load than the same carpet would in a dry climate.
We use truck-mounted hot water extraction – the method carpet manufacturers specify – which pulls out embedded soil vacuuming can’t reach and leaves less moisture behind than rental units do. That matters in a damp climate: the CRI notes that properly extraction-cleaned carpet should be dry within 12 hours, which is well inside the window where dampness becomes a mildew problem.