LOAD AND RUN BOX GUTTER CALCULATOR
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MINIMUM WIDTH = 300 mm for Commercial construction, and 200 mm for Domestic consruction.| Material | Base Metal Thickness (mm) | Max Length (metres) | Minimum expansion space (mm) | To use Rectangular DP (mm*mm) | Enter Equivalent circular DP dia(mm), To find RWH sizes | |
| Aluminum | 0.90 | 12 | 50 | 100 * 75 | 97.5 | |
| Copper | 0.60 | 9 | 50 | 100 * 100 | 112.5 | |
| Copper | 0.80 | 15 | 50 | 150 * 100 | 137.5 | |
| Copper | 1.0 | 26 | 50 | 125 * 125 | 140 | |
| Steel Colorbond Zincalume | 0.55 | 20 | 50 | 150 * 150 | 168 | |
| Steel | 0.75 | 25 | 50 | |||
| Stainless Steel | 0.55 | 20 | 50 | |||
| PVC | - | 10 | 30 | |||
| Zinc | 0.80 | 10 | 50 |
Instructions & Notes:
This program incorportes a simplified version of calculating the roof cachment area, and makes no allowance for rain shadow effects.
Hence it is perfect for a box gutter with roof on one side only and no vertical faces.
If it is used with a roof entering from both sides, or with a small vertical face or parapet, then the result will have a slightly
greator factor of safety than would otherwise be allowed. This is because the possible rain shadow effects have not been subtracted from the
total catchment area. However this is normally advantageous, as it allows for construction tolerances, and unusual rainfall events etc.
Also, This calculation is only suitable when the box gutter drains to a rainwater head, (with overflow) at the end of the box gutter, as shown.
For other conditions, eg a sump somewhere along the length of the box gutter, a separate formula applies, usually resulting in a larger gutter.
Click on the OTHER HYDRAULIC CALCULATORS link below.
Choose a trial width of box gutter (minimun width is 300mm for commercial or 200mm for domestic). If this gives a depth of Box Gutter that is too deep for the
roof consruction, try a larger width, etc etc.
Then press the calculate button.
The most efficient hydraulic shape is width = twice depth.
This calculation also gives a suggested trial size for the downpipe, which is needed for the rainwater head design.
Rainwater head design:
Enter the closest available DP size to the trial DP size calculated by the first button. Don't go too much smaller.
Use trial and error of all variables to obtain a result that suits the construction.
IMPORTANT NOTE
The code only allows for flows up to 16 litres/sec total runoff in the Down pipe. It recommends
that if this figure is exceeded, more downpipes should be added, or catchments reduced.
The graphs in the Code were confirmed by experimentation only up to a flow of 16 litres/sec, and for this reason do not go beyond this flow.
However my calculators are based on standard hydraulic formulas, weir, orifice, trajectories, open channel etc with the constants adjusted
to give an answer consistant with the code. For this reason I believe that my formulas will stay true regardless of the flow.
However, just bear in mind that if you use flows above 16 litres/sec you are beyond the scope of the Code.
I would also be interested in any modifications, or suggestions that you would
like incorporated.
If you need more info, or you would like other areas of Australia, or New
Zealand, added to the list, please send me an email.
Click here to send email
Regards
Ken Sutherland
B.Tech MIEAust CPEng RPEQ
DISCLAIMER: It is the users responsibility to ensure input data is calculated and entered correctly, and that the program is
suitable for the roof configuration required.
OTHER HYDRAULIC CALCULATORS