Dave
If you should ever happen to buy a universal 15 meter hose, you can cut it to any length you like and then attached the hose-ends for your particular model of cleaner. At it's best, you can put the cleaner at ground level and the take the hose 15 meters in any direction. 40 feet would be just over 12 meteres long, not forgetting that with a backpack cleaner you'll need 40 feet of flex at least (unless such a thing as a rechargable version exists?). I'm confused though as i thought youy said they were 3 metres high?