The overflow diameter is the same as the downpipe diameter.
Box gutter sump size.
Sump with a side overflow device sumps do require an increase in the depth of flow in the box gutter and gutters are to be fitted with either.
The code sump length is 600mm.
Sumps are usually attached between a box gutter and the downpipe.
Experiment with this figure to get the depth of box gutter you require.
Overflow devices need to discharge to the atmosphere in such a way as to prevent damage to buildings and property.
The depth shown of the box gutter is the depth at the upstream end.
However if you choose to go above 16l s the downpipe may get larger than 150 dia.
This will give a sump depth about 150mm.
Choose an available dp size or any other size and enter that for the calculation of the sump.
The minimum size of a sump is 400mm x 200mm minimum width of box gutter and 150mm deep.
Flow as the down pipe.
If draining to a sump with a vertical overflow in the middle of the box gutter use this calculator.
Trial box gutter width the minimum width allowed for commercial projects is 300mm for domestic projects 200mm.
The rectangular overflow width is equal to the box gutter width less 100mm.
How much fall should i have on a box gutter.
The gutter collects the water and disposes of it through the drainpipe.
Sumps can be made to order but are commonly manufactured in either 100mm and 150mm depths.
For the associated box gutter outlet.
A box gutter is given its name as it is usually boxed into the middle or edge of the roof.
Colorbond box gutter measures 150mm x 150mm x 150mm.
They collect storm water before it is carried away by the downpipe and they also serve to catch any debris before it enters the downpipe.
The outlet must be no further than the diameter of the outlet to the centre of the outlet.
50mm clearance on both sides.
The suggested down pipe diameter is shown for reference purposes only.
Deviations from the gradient must be smooth and prevent towards the outlet without a proportional permanent ponding.
If this is the case the sump length will increase to accommodate the downpipe.
Where there is more than one overflow the design flow is divided equally and the spitter size shown will also be the suggested dp size for this fraction of the flow.
