Measuring Round Grates
See below Fabco’s instructions for measuring round grates.
The first measurement required is the DIAMETER of the grate. In order to get this measurement you need to remove the grate from the frame.
Next we need to measure the DIAMETER of the CLEAR SPACE inside the grate support ledge. A close up of the grate support ledge is shown in Step 3. The Fabco catch basin insert features a circular supporting flange that is designed to fit on this ledge. The maximum diameter of this support flange needs to be slightly less than the diameter of the grate. And the physical diameter of our filter must be less than the area of the CLEAR SPACE. The unit hangs down inside this clear space.
The circular grate support ledge supports the Fabco unit. Once the Fabco unit is in place, the grate is re-installed directly on top of the Fabco unit. Any water entering the grate will flow through the Fabco filter.
The following image shows the bottom surface of the grate. In most cases cast grates have ribbing on the bottom surface that extends downward. This ribbing provides extra load bearing strength. In this image the rib is central and is located next to the measuring tape. There are three critical points to be aware of:
1) Is there ribbing?
2) Does the rib height taper to the grate edge like the one shown or does it hold its height from edge to edge?
3) What is the distance from the rib edge to the outside edge of the grate? In the photo this is about 1″.