Rectangular or circular downpipes.
How many downpipes per square metre of roof.
Doubling the number of downspouts halves the required capacity for each.
The example s gutter and downpipes have been calculated as compliant to harvest a maximum factored roof area of 47 square metres.
Using clause e1 table 5 see figure 2 at a roof pitch of 45 for this example.
This is because larger roofs require bigger volumes of water to be diverted away from them during periods of rainfall.
The rainwater is guided through downpipes into a sewer other disposal point or collector.
Total roof area 50m2 serviced roof area 25m2 flow capacity 25 x 1 67 41 75l min min gutter area 41 75 0 0016 0 8 3413 73mm2 with a centrally located outlet all marley spouting profiles could be used.
To calculate the minimum number of downpipes divide the roof catchment area by the allowable maximum catchment per downpipe.
Select 100 x 50 rectangular downpipe.
63 mm diameter downpipes serve roof plans up to 35 m 74 mm diameter downpipes serve roof plans up to 50 m.
Min number of downpipes roof catchment area.
In general gutters are available in different forms and numerous applications such as suspended gutters box gutters valley gutters etc.
Requires flow to be calculated in one of the other calculators.
Allows for any shape of rwh.
A square inch of downspout can drain 1 200 square feet of roof during a rain with an intensity of one inch per hour.
Determine minimum number of downpipes.
The number of downpipes you need will depend on the size of your roof and your chosen style of guttering.
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The roof slope as per the code should be 12 5 deg.
From figure 3 5 a in as nzs 3500 3 the maximum catchment per downpipe is 47m 2.
Therefore 74 mm downpipes are.
The downpipes are sized to suit the roof area as well as the roof pitch so.
This free roofing calculator estimates the area of a roof and the amount of materials required to replace or build said roof.
Therefore the user should calculate the perimeter of the square.
How many downpipes and what size.
If a square outlet is against a wall only 3 sides will accept the flow under weir flow conditions.
Rectangular or circular spitters any number of circular spitters and reduction in down pipe size by using a funnel section.
Down pipe size not listed a few of the uncommon pipe sizes are not listed eg sizes smaller than 90mm 125mm dia etc.
Gutters are produced in many variations and their use is various.
Areas a and b require 74 mm diameter downpipes and area c requires a 63 mm diameter downpipe see figure 2.
