If there are 3ft tress growing out then we dont do the job at all. You have to be selective with the jobs you take on as the Lance cant break down years and years of moss and roots.
The secret of breaking the debris down into pieces that flow down the downpipe for you to collect at the botton is to work away fron the downpipe entry point in about 6" chunks. The lance and water flow should be towards the downpipe and at an angle of 40% to your body. Flush that section,move away and do the next bit.
If the debris is not too much you can get away with bigger chunks.
Phew- does that make sense.

Its like wfp, its not suited to all applications but we manage to do about 80% of the work we are asked to quote for with it.
Sarah