What Is A Roof Drain?

The Plumbing Code Definition

OK, so what is a roof drain and how is it different from other drains? Well, let’s take a look at the authority on the subject which is the uniform plumbing code. 

Zurn Z100 primary cast iron roof drain

It reads as follows: “ROOF DRAIN: A drain installed to receive water collecting on the surface of a roof and to discharge it into a leader, downspout or conductor.” I would have been a bit more specific on the description as the roof drain generally receives rainwater, but not just rainwater, and it is usually on a flat roof. Pitched or sloped roofs use gutters for rain water conveyance. 

Ok, but what is a leader? Or a downspout or conductor? This is specific jargon to the plumbing and/or construction trade. But here goes:

  • leader– this is defined as “an exterior vertical drainage pipe for conveying storm water from roof or gutter drains”.
  • conductor: a pipe inside the building that conveys (moves) storm water from the roof  to a storm drain (at ground level) or a combined building sewer (storm drain and sewer together) or other approved point of disposal. roof drain leader,roof drain
  • More words…what’s a gutter. A standard dictionary definition is: a shallow trough fixed beneath the edge of a roof for carrying off rainwater. 
  • So the roof drain receives the rain water and the leaders, conductors (vertical) and gutters (horizontal) will covey (move) the water to the ground. 

What are flat roof drains made from?

UPC (uniform plumbing code 1102.1). Roof drains shall be constructed of aluminum, cast iron, copper alloy of not more than 15% zinc, leaded nickel bronze, stainless steel,ABS, PVC, polypropylene, polyethylene, or nylon and shall comply with ASME A112.3.1 or ASME A112.6.4.  

All of the roof drains on the market comply with these requirements. If you find one that doesn’t, don’t use it. 

Dome strainers required

Roof drains shall have domed strainers. Exception: roof drain strainers for use on sun decks, parking decks, and similar areas that are normally serviced and maintained, shall be permitted to be of the flat surface type. Such strainers shall be level with the deck. 

Dome strainers are included with the roof drain. Manufacturers provide a choice in materials generally as a special order. These can be made from aluminum, stainless steel, brass, ABS, PVC (plastic). Review their specs for the exact offering. 

Roof drain flashings

This is important….more to come

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