Hydraulic ram pumps and Sling Pumps

7. Gutters and downpipesThe efficiency of any rainwater catchment depends to a great extent on the gutter and downpipes.Qualified tinsmith's (or plumber's) work is demanded to fix gutters for catchment. Large roofsespecially need precise workmanship. Often workers are seen using ladders, rather thanscaffolding, but precise gutter fixing cannot be achieved without a scaffold on the overall length ofthe cave.The slope of gutters should be about 0.3-0.5%. This first of all requires precise measuring. Howeverin rainwater catchment, a slope of 0.3 -0.5% often remains theory. As an example: an eave length of30.0 m would require an overall slope of 90-150 mm from the end to the outflow. But gutters fixed 90mm below the eave are likely not to catch heavy runoff. Under normal circumstances the problemwould not occur as one would furnish a roof eave of 30.0 m with at least three downpipes. Thiswould not only solve the problem of sloping but also reduce the size of the gutter, as the catchmentarea per outflow is much smaller. In rainwater catchment maximum runoff is to be drained into thereservoir and compromises must be made.After scaffolding has been erected under the roof overhang, the eave must be checked to see if it ishorizontal. Sometimes this is not the case, particularly with long roofs. To measure and compromisethe slope a thin wire is to be stretched tightly along the length of the eave and attached to a nail onboth ends. If this method is used, a 50-mm overall slope could be obtained for the gutter. This isadmittedly next to nothing. However the system will also work if the gutter is absolutely horizontaland straight. Whatever minimum slope can be achieved this first of all serves the purpose to ensurethat there will be not even the slightest slope in the opposite direction. Large gutters are usuallysquare. They should not be fixed on horizontal brackets but have a slight slope toward the outside(see drawing No. 8). This means viewing the cross-section of the gutter which must show aminimum slope from the eave corner toward the opposite corner. This will help to increase the rateof draining.A common mistake observed is the underdimensioning of the gutter bracket. It has to be kept inmind that during heavy downpours gutters can suddenly be filled with water and their weight mightincrease up to 40 kg/m. To avoid deformation or even collapse of large gutters, brackets must bestrong and at distances not exceeding 1.0 m. Brackets for large gutters should never be fixed onpurlines only. If the distance between the rafters makes an intermediate support necessary there aretwo ways of solving the problem. One is to have two different strong types of brackets, the strongerfixed at the rafters, the weaker ones at the purline in between the rafters. The other, often easier,method is to exchange the purline for a much stronger and larger one.t14In rainwater catchment downpipes often channel the water over long distances (from one gable sideto the other) with a slope of sometimes only 1.5%. In all those cases they are not working asdownpipes but rather as covered channels. As a result the downpipes sometimes develop a weightsimilar to the gutters and must therefore be securely fixed to the wall. Usually downpipes are ofsmaller dimension than gutters since water falls more or less vertically. In rainwater catchment thisis often not the case and downpipes should be of the same dimension as the gutters they are linkedto.Reservoirs at public buildings are often large and, so as not to block the passage, sometimes morethan 2.00 m away from the building. In those cases the downpipes must be bridged from the buildingwall to the tank inflow. It is necessary to suspend the bridged downpipes or to support them.Suspension is done if the wall above the bridge point is high enough. A steel clamp must be putaround the downpipe in the centre of the pipe bridge and this fixed by a steel rope with a stronghook plugged into the wall. This has to be done in such a way that gable wall, pipe bridge and steelrope form a triangle. If it is not possible to suspend the pipe bridge, it must be supported. This isdone by fixing a welded triangle of steel angles at the wall underneath the pipe bridge. Any pipebridge must at least be supported or suspended in the centre if it exceeds 1 m in length.81