Measuring Rectangular Grates

Treating stormwater runoff at the source with a catch basin insert filter is a cost-effective treatment option.

Measuring rectangular grate for Fabco catch basin insert Fabco’s StormBasin, StormSack, StormSok and StormPod are catch basin filters that can fit most storm drain configurations. These filter products are designed to be installed under the grate of a typical storm drain inlet. Fabco catch basin insert filters can treat a variety of pollutants just beyond the curb, effectively cleaning the water before it exits downstream.

Knowing the correct physical dimensions of a storm drain is critical to successfully installing a catch basin insert filter. Many drain inlets are square (or rectangular), flat, or drop inlets. To properly fit a catch basin filter to a grate and frame, measurements should be within a 1/16”.

When measuring rectangular grates, follow the guidelines below:

Step 1:

Measure the overall grate dimensions inside the frame. In the example above the grate is 24” x 24” square.

Step 2:

Measure the CLEAR SPACE inside the grate support ledges. In the example above this is 22 ½”. This grate and frame combination is square so the clear space is defined as 22 ½” x 22 ½”. When an insert is installed into the frame its support flanges rest on top of the grate support ledges. The unit then hangs down or is suspended from the flanges below the support ledges and occupies most of the available clear space.With round and square StormSok and StormPod products the clear space measurement is critical as these units have a fixed support flange size.

While you are measuring the clear space it is important to examine the walls of the drain (all 4) directly below the frame. The first 20” below the ledges are most critical. Any object that extends from the wall beyond the edge of the support ledge could interfere with the device. This could include: pipes, traps, concrete and brickwork. These points of interference would need to be trimmed back if possible at the time of installation.

Step 3:

Measure the depth of the drain from the bottom of the support ledges to the vault floor.

Step 4:

Confirm whether the grate has ribbing that extends downward from the bottom side of the grate. In the example above, both grate images display vertical ribs that extend down.

Fabco also has instructions for measuring round grates.