Key Terms in Commercial Roof Drain Systems and Parts

Learning the lingo of what industry professionals use in commercial roofing and drain systems helps in ensuring the drain you end up purchasing is right for your needs. These are a list of key terms that are commonly referred to in commercial and industrial roof drain systems.

When investing the time to find the right drain system for your building, any of these key terms may come up in conversation and it’s always important to know what is being discussed.


Bolt-to-bolt is a measurement, typically communicated in inches, providing the distance from one bolt to the next. When a 3-bolt or 5-bolt ring is being measured, the bolt-to-bolt measurement comes from one bolt to the following, as it appears circling the ring. When discussing a 4-bolt drain, the bolts are measured directly across from one another.

Cornice drain

This is the type of small-diameter drain that mounts onto the deck of a roofing system. It is generally employed in combination with channels or scuppers.

Drain dome

Also sometimes referred to as the ‘drain strainer’, ‘drain basket’, ‘drain cover’, or ‘birdcage’, the drain dome is used to control the amount of liquid in the drain. Placed directly on top of a drain, a dome is also used to keep larger items from clogging the drain.

Drain ring

The drain ring is also sometimes called a ‘clamp collar’, ‘clamp ring’, or ‘flashing ring’. Typically metal, it is used to secure the roof drain to the roof deck.


A boot is a unique invention used to convert and connect a drain’s downspout to the storm system.

Downspout nozzle

Attaching to a sleeve, a downspout nozzle provides a drainage pathway from a roof’s drain to the downspout. Some roofing contractors refer to a downspout nozzle as a ‘cow’s tongue’.

Gravel stop

The gravel stop is a key part of the drain ring. Situated on the outside of the drain, it may be recognized by the ‘V’ notches that sit in it.

Inside diameter

Inside diameter, or more commonly referred to simply as ‘ID’, is a measurement of distance. It identifies the distance between the inside edge of the gravel stop to its opposing edge. Why the ID is key is because it helps to identify the drain dome required for a roofing project.

Outside diameter

Outside diameter, or more commonly referred to as simply ‘OD’, is a similar measurement of distance, this time between the outside edge of the drain ring to its opposing edge.

Parapet sleeve

A parapet sleeve is a drainage pipe specifically designed to fit through a parapet and then to a downspout.

Parapet drain

Also sometimes referred to as a ‘scupper drain’, this is mounted where the rood deck and building wall intersect.

Sump receiver

Also known as a ‘deckplate’, this product is used to mount the roof drain bowl to the roof. This can be done one of two ways – through direct attachment to the drain or through the use of an underdeck clamp.

These are some of the basic terms that may come up in conversation when discussing purchasing a commercial roof drain system. Buying roof drains or replacement parts should always be done with careful consideration of the specific type of drain system your building can accommodate.

2018-09-19T13:44:12-04:00February 7th, 2018|LexGoShop Blogs|