Gutters are intended to collect water from a roof and take it to downpipes. These may meet at funnel-shaped containers, called hoppers, and from here the water flows down to a drain. A surprising amount of other debris is washed down with the water and hoppers may become choked with nests and growing plants.
Before cleaning is started, place a bowl under the downpipe to prevent rubbish blocking the drains. Scrape inside the gutters with a piece of wood cut to a slightly smaller curve, then brush loose dirt into a bucket. A rod can be pushed through a straight downpipe. At a hopper head lift out rubbish, rather than pushing it further on. In a bad case it may be necessary to dismantle a downpipe to clear separate sections.
Check the joints and remake them if necessary, by refilling with mastic. Plastic guttering does not need any special treatment, but rust can be removed from iron guttering with a wire brush and the insides should be treated with bitumastic paint. Treat the outside of the guttering to match other painting. Look at the roof and remove moss or anything else likely to wash down and block the gutters
later. Cages can be bought to fit over vent pipes and hopper heads to prevent blocking. Pour water into the gutter at its highest point to check the flow and wash through any remaining dirt.