| 摘要 |
Embodiments include controlled flow rood drains which minimize the size of drainage piping and meet established maximum flow rates by draining built-up water from a flat roof. Embodiments are pre-set by the manufacture in terms of the diameter of the standpipe orifice, which controls maximum flow rate at a predetermined depth of water on the roof, and the height of the standpipe, which determines the depth of water on the roof. Embodiments resist alteration of the flow rate by vandals, tenants, or managers of the building, and are resistant to flow which bypasses the drain control and resistant to plugging by roof debris or snow. |
| 主权项 |
1. The process for determining the size of the orifice of a drain which controls the rate of drainage of water from a flat roof comprising the steps:
a. obtaining a drain comprising a cup-shaped body having a connector for connection of the body to a drain pipe, a disk-shaped collar with a hole in the center of the collar, the collar attached to the top of the body, the collar attached to the roof, a standpipe with a first and a second end, the first end of the standpipe open, the standpipe having a circular orifice in the side of the standpipe near the first end, the standpipe connected by the first end coaxially to the hole in the collar, the lowest portion of the orifice on the side of the standpipe approximately at the level of the collar, and a grated dome attached to the body, the drain attached to the roof with the collar level with the surface of the roof, wherein the height of the second end of the standpipe above the collar is the same as the maximum allowed depth of water on the roof, b. determining the allowable drainage rate for the roof, c. determining the roof area for an individual drain, d. determining the drain down rate in GPM for each drain based on 100 year expected rainfall for the location of the roof and the maximum build-up, and e. calculating the orifice size based on the required controlled flow GPM per drain using the formula: Q=448.8×K×A×√2gh, when Q=controlled flow GPM per drain; 448.8=conversion factor from cubic foot per second to GPM; K=orifice constant=0.512; A=orifice area in square feet; g=specific gravity of 32.2 ft/sec2 and h=head at orifice in feet. |
