From a previous job. We'd order replacements for a machine once it had about 1200 hours on it. By then, suction would be down about 5% using something like this...
http://compare.ebay.com/like/2808195451 ... si=y&cbt=y and
http://www.ebay.com/itm/Extech-AN100-CF ... 4ab768f885
By the time we hit 1500 hours, it may be down 15-20%, which you will notice in the feel of the wand and on the carpet. Generally if one or both vacuums was under performing by 20%, that was the end. At first it is imperceptible. Then one day you actually start thinking the rugs seem damper and the wand pulls easier, or sometimes you don't. I used to pull a
EDIC Polaris 1200 up and down the halls of various buildings. This was a 19" self contained beast. Liked the machine a lot. Going to pull the trigger on a new
EDIC Polaris 1201PS (its replacement) in a month or so. Just want to nail down one more large area commercial contract. I never noticed it losing suction. Someone from the service department just checked it because it needed a new brush. Supposed to pull something like 85" per motor, so 70" was retirement. One was pulling about 55" and the other about 60". We probably could have squeezed one or two more jobs without anyone being the wiser. Once new vacs are in, the result is always very obvious. Now I have no such tools and just do it when dissatisfied with results until I can afford toys.
