The sole width of the box gutter is not to be reduced towards the outlet without a proportional increase in depth.
Box gutter sump depth.
2015 3 7 4 layout e for the sump high capacity overflow device the depth of the sump hs shall be not less than 150 mm regardless of the position of the normal outlet.
Discharge through either a rainhead or sump.
Figure 1 as an alternative the top of the rainhead may be installed so that it is no higher than 50 per cent of the flow depth of the box gutter consistent with saa hb39 installation code for metal roof and wall cladding section 5 clause 5 7 3 and figure 5 7 3to prevent internal flooding or damage to the building or contents see figure 2.
The depth shown of the box gutter is the depth at the upstream end.
Choose an available size or any other size and enter that for the calculation of the sump.
Have a sole width which is not reduced discharge at the downstream end without.
Have a minimum depth of 75mm at the high end.
Have a minimum width of 300mm for commercial installations 200mm for domestic installations.
Choose an available dp size or any other size and enter that for the calculation of the sump.
All domestic box gutters must be a minimum of 200mm wide and 75mm deep.
The suggested down pipe diameter is shown for reference purposes only.
This is a good size for the required flow.
This will give a sump depth about 150mm.