This table is based on zurn s roof drain vertical requirement for horizontal roof areas at various rainfall rates table.
Flat roof drain cover.
Those roofs benefit from siphonic drainage systems.
Gravity drainage systems are only recommended for flat or low slope commercial roofs that have a surface area of less than 150m 2 per drainage point.
Most strainers or domes that cover a drain on flat roofs are poorly designed because they block smaller debris and the strainer becomes clogged preventing any water flow.
There are three types of drain systems on a flat roof.
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Replaces popular 10 inch plastic strainers domes.
So often we find that inner drains are high on the roof causing water to pool around them.
Take the roof s total square footage and divide by the total square footage handled by one drain.
Calculate drains needed.
It is very critical to position drains for maximum effect.
Twigs seashells and rocks should not be able to get through strainer holes or slots.
Roof drains parts accessories floor drains parts accessories downspout nozzles adaptors couplings fittings backwater valves parts accessories carriers and fixture supports cleanouts access covers flanges parts accessories floor sinks parts accessories fluid controls hydrants interceptors shower drains parts accessories specialty products stainless steel drains value.
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10 inch plastic roof drain dome strainer grate 3 hole yellow portals 67111 10 inch yellow polyethylene drain dome strainer grate.
Larger roofs collect more water that may not drain quickly enough with just a gravity system.
The above sizing data is offered as a guide only.
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Old style drain strainers.
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Most draining systems on flat roofs have a poor design or are not correctly installed.
These types of objects will cause blockage in drain pipes.
9 1 2 od base x 4 1 4 high with 3 bolt mounting holes.
The result is the number of drains needed.