Truckmounts have very high flow pumps fitted. As Mike says sometimes when doing greasy carpets such as pubs and restaurants the water pools on the top. The carpet won't shrink either. We used to pour buckets of red hot water with Enzall over black tops and leave it to dwell and sometimes clean them 3-4 times to get the desired result. These were usually the entrances to the bars and kitchens. Axminsters are very forgiving will usually relax back to their original dimensions, provided they have been seamed correctly.