# Frequent question: What is a secondary roof drain?

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The secondary roof drains can be of two types — roof drains with an independent piping system or roof drains that combine with the primary roof drainage piping, which will require an increase in piping size.

## How do I know how many drains my roof has?

Take the roof’s total square footage and divide by the total square footage handled by one drain. The result is the number of drains needed. For example: 50,000 / 4,400 = 11.36; or 12 drains required.

## Do you need an overflow roof drain?

Overflow drains, located 2 inches (51 mm) above the roof drain inlet, are required by Section 1506.3 where parapets or other conditions will cause ponding if the roof drain is inoperative. … The lower edge of the overflow scupper opening shall be 2 inches (51 mm) above the roof drain.

## How does an overflow roof drain work?

It allows the water to pond on the roof a maximum of two inches before coming into service. This is a plumbing code requirement. The overflow or backup roof drains protect the flat roof from caving in under the weight of standing rainwater should the main drains become clogged with debris.

## How many drains do I need for a flat roof?

It is important to remember that no roof area should ever have less than two roof drains. Size and placement of rooftop equipment may necessitate additional roof drains. Consideration should also be given to local codes whish may require separate overflow drain systems.

## What size drain is needed for a 5000 square foot roof?

According to the chart, for 1/8” slope per 12” of pipe, for 5,000 square feet of roof area, with a 6” per hour of rainfall, the required pipe size is 8”. To size the vertical roof drain for the same parameters – 5,000 square feet of room area and 6” per hour of rain – consult Table 1106.2(Figure 3).

## How much water can a roof drain handle?

Example: For a 4″ hourly rainfall and 4″ leader, each drain can handle 4,600 sq. ft. of roof area.

## Where should a roof drain be placed?

Location – Drains SHOULD NOT be next to other rooftop objects like A/C units, vent pipes, or skylights. Level – Drains SHOULD always be installed at the lowest level of the roof surface. Strainers/Domes – Drain strainers SHOULD have holes or openings large enough for small debris to pass through.

## Do roof drains need to be insulated?

Insulation should be provided on all piping, especially on commercial projects but also on residential jobs. … Storm water piping is also susceptible to condensation and should be insulated from the roof drain bowl to a point where the piping turns from horizontal to vertical.

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## What is the height of an overflow drain above a roof drain?

Roof drains and overflow drains, except those draining to hanging gutters, shall be equipped with strainers extending not less than four (4) inches above the surface of the roof immediately adjacent to the drain.

## Where roof drains are required secondary roof drains or scuppers may be provided?

Where roof drains are required, secondary (emergency overflow) roof drains or scuppers shall be provided where the roof perimeter construction extends above the roof in such a manner that water will be entrapped if the primary drains allow buildup for any reason.

## What is a roof drain leader?

In plumbing, a pipe installed to drain water from the roof gutters or roof catchment to the storm drain or other means of disposal. Also called a conductor, downspout, or roof drain.

## Whats a roof drain?

A roof drainage system is a system that is installed on the roof to divert water and debris off the roof. Many people ask, “What are roof drains called?” and they are simply called roof drainage systems. The drainage system starts at the roof line and then you have roof drainage to ground.

## Where do flat roof drains go?

These drains are placed in areas of the roof that collect the most water, and they lead the water into a system of pipes that is installed below the roof. The water travels through these pipes until it is dispensed into a gutter or downspout at the side of the building.

## What are flat roof drains called?

Scupper drains – Another kind of drainage that you can have your roofing contractors install on your flat roof are scupper drains, which are open holes that are cut into the roof’s edge. When you install a scupper drain, the roof will be sloped toward the scuppers to drain water through them.

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## How does water drain off a flat roof?

What do Drainage Systems do? A low-slope roof tilts slightly downhill from its center or from one side, so water rolls off to parapet scuppers and down the hopper (downspout). The scuppers are the openings in the outside walls, specifically designed to allow water, but not debris, to wash off your roof.