Where you can drain over the wall the overflow drain must be at least the same size as the regular drain and located no more than 2 above the low point of the roof.
Overflow roof drain design.
In addition to the primary roof drains there will also be overflow drains which are used for redundancy and sized in the same manner.
Roof drains from zurn include combination primary overflow control flow dual outlet siphonic retrofit and more which cater from educational to commercial needs.
This type of pattern is particularly useful on buildings that are easily divided into rectangular areas.
These drains are distinguished by having higher rims.
The premise of the pattern is that a drain is positioned in the center of the rectangular area and there is a four way positive slope into the drain.
While you must provide the overflow it can not be connected to a downspout.
You also must include half of the area of any vertical walls that may divert rain to the roof.
Where you must drain through the wall with a scupper the overflow must be three times the required size of the roof drain and have a minimum height of 4 and again be installed no more than 2 above the roof low point.
Scuppers shall not have an opening dimension of less than 4 inches.
The most dependable type of roof drainage design is the inverted pyramid pattern.
The secondary drain is typically placed about 1 2 above the depth of water above the primary at its design flow.
In determining the maximum possible depth of water all primary roof drainage means shall be assumed to be blocked.
As we will see in steps 3 4 the size of the roof drain lines is dependent on the square feet of the roof area being served by each roof drain.
Properly designed roof drain must have the following features.
Roofs shall be designed for the maximum possible depth of water that will pond thereon as determined by the relative levels of roof deck and overflow weirs scuppers edges or serviceable drains in combination with the deflected structural elements.
Roof drains watts roof drains provide flexible solutions for specifiers and installers in any commercial roof application.
3 398 380 540 380 5 3 06 in order for the 6 drain to handle the necessary flow there will be a depth of 3 06 of water above the primary drain at its peak design flow.
Pleasing dome shape with a low profile and adequate free drainage area corrosion resisting dome material effective debris protection overflow drainage to allow drainage during debris build up gravel stop positive flashing clamp seepage control channels.
