TDS Drainage Glossary

90 Degree / Turn

Many trench drain systems offer options to include a turn or 90-degree angle. Some offer a 90-degree angle as a separate section but some have systems that require modifications. In these cases, you may have options to cut a mitered angle along the channel and grate or cut a section to assemble one channel to the top/side of the next channel instead of a miter cut. Some systems have round knockouts that allow for pipes to be assembled so that the turn is achieved with a Schedule 40 pipe underground that leads to the next channel.


American Association of State Highway and Transportation Officials – is a standards-setting body that publishes specifications, test protocols, and guidelines that are used in highway design and construction throughout the United States. Many airport and highway drainage projects must meet guidelines established by AASHTO.


The Americans with Disabilities Act (ADA) states that grates in walking areas have slot openings no larger than 1/2″ in size in one direction. This measure allows for wheelchairs to safely cross grated areas. This measure can also be applied to areas that will see bicycle traffic.

Angle and Grate

This system has a variety of terms associated with it such as frame and grate or rail and grate systems. It consists of two 90-degree rails that are installed when a trench drain is formed with the intent of providing a lip or ledge for the trench drain grates to sit on. The frames also allow for locking devices to be used to hold the grates in place. These systems can be made of any number of materials but are typically made of cast iron, fiberglass, or a combination of materials. Click here to see an installation guide for a fiberglass frame and grate system.


American National Standards Institute is a private non-profit organization that manages the standardization of processes, services, personnel, and products in the US. Grate Load Classes are defined as:

Light Duty
All grates have a safe live load (as calculated in paragraph 6.1.6 of the ANSI Standard) under 2,000 lbs. (900 kg.) For pedestrian foot traffic only.

Medium Duty

All grates have a safe live load (as calculated in paragraph 6.1.6 of the ANSI Standard) between 2,000 lbs. (900 kg.) and 4,999 lbs. (2,250 kg.)

For light pneumatic tire traffic only. Sidewalks and residential parking.

Heavy Duty

All grates have a safe live load (as calculated in paragraph 6.1.6 of the ANSI Standard) between 5,000 lbs. (2,250 kg.) and 7,499 lbs. (3,375 kg.)

For commercial pneumatic tire traffic patterns and tractor-trailers.

Extra Heavy Duty

All grates have a safe live load (as calculated in paragraph 6.1.6 of the ANSI Standard) between 7,500 lbs. (3,375 kg.) and 10,000 lbs. (4,500 kg.) For forklift traffic. Roads and Highways. H-20 Load Rated.

Special Duty
All grates have a safe live load (as calculated in paragraph 6.1.6 of the ANSI Standard) over 10,000 lbs. (4,500 kg.) For airport traffic.

Baked on Oil Finish

With a strong background in metallurgy and geology, Trench Drain Systems has created a precise technique that provides an advanced patina on cast-iron grates. Cast iron, in its natural state, may arrive in a gray or silver color but will immediately begin to rust with exposure to any moisture leaving a bright orange finish. Through a series of baths in water and oil, along with literally baking grates in an oven, the end results are grates that have a chocolatey brown patina similar to what you see in parking lot grates. Learn more about our BoOF process.

Bar Grates

Bar grating is a term that is indicative of heavy-duty grating that usually has a variation of a grid pattern with large grate openings or flow areas. They are available in a variety of materials but are commonly available in cast iron, fiberglass, and stainless steel.

Bicycle Safe Grates

Drain grates can create a number of hazards for bicyclists with sinkholes around frames, raised frames, wide longitudinal slots, or gaps between frames and grates. If you are working on a project that requires grates that are safe for bicycle traffic; we recommend looking at ADA-compliant trench drains and grates. If they are safe for wheelchairs, they are safe for bike tires.

Bottom Outlet

A bottom outlet is simply an opening in the bottom of a channel drain to allow the flow to exit below the drainage system. They are typically connected to a Schedule 40 pipe. Many trench drain systems provide either a special adapter to accept a bottom outlet or an area on the channel is marked or embossed with a knockout to facilitate drilling an outlet to accept a pipe. Click here to see examples of bottom outlets. 

Bronze Age Decorative Grates

Trench Drain Systems offers an exclusive selection of decorative grating called Bronze Age Decorative Grates. These grates are made of aluminum, bronze, and stainless steel with over a dozen different patterns. At this point in time, the majority of the grates in this line are compatible with the 3″ NDS Mini Channels and the TDS MAX Mini drainage system but also include round point drain grates as well.