Jobs with mainly silt are near to the coast,moss and barnicle type scabs on tiles get washed into the gutters and end up as or like silt,some jobs I’ve just used the Gardiner gutter jet it clears a hell of a lot of gutters to an acceptable standard. I don’t go after gutter work I’ve past no end of work onto a chap I use,it’s a dirty horrible job using a vac in a lot of cases.