1010 and 1080 Large Capacity Roof Drains

by JRSBlogWriterMarch 20, 2013

jerry engineeringPlease see below for submittals for fig. nos. 1010 & 1080 large capacity roof drains. The large capacity is in reference to 8, 10 and 12 in. outlet sizes. These roof drains are shown on the back sheet of the 1010, 1020 submittal. In recent years, these larger sizes have become popular with specifiers.

The flange diameter is 20 inches. It is our recommendation to always use the 20 in. diameter flange for the 8, 10 and 12 inch outlet sizes. The larger sump will flow a higher volume of GPM. Considering the amount of roof square footage the drain will be handling, the flow will be considerable. The other important reason is the free area of the dome. The plumbing codes require the free area to be 1½ times greater than the free area of the drain outlet. We prefer the free area to be 2 times greater than the drain outlet. The 12 in. outlet is only provided with a 20 in.flange and only with a no-­‐hub connection.

The 1080 roof drain with external water dam submittal is also attached. It is also available in 8, 10 and 12 in. outlets. The same information above applies to the large capacity 1080 roof drains.

Please contact Sales Engineering if you have any questions regarding these roof drains.

Large Capacity Roof Drains

Some engineers have standard details recessing the area where the roof drain is located. Caution should be taken not to create too deep of a recess where the emergency overflow drain will be compromised.


Please refer to the photo above. What is wrong with this installation? The primary roof drain (1010) and emergency (secondary) overflow roof drain (1080) are provided per code.

The code states the overflow roof drain shall be a minimum of 2 inches above the roof. The maximum height of the water dam shall be a height to prevent the depth of ponding water from exceeding that for which the roof was designed to handle. By recessing these drains, the recessed area will become flooded and the overflow roof drain upon becoming submerged during high volume of rainfall and will discharge giving the false perception that there is a problem with the primary roof drain. In this case, the water dam collar should have been extended higher. Higher water dam collars are available.

Visit the 1010 and 1080 product pages to view the submittals and installation instructions.

Download the original newsletter here: Vol. 3, Issue 2: 1010 and 1080 Large Capacity Roof Drains