How to Measure Roof Drain Parts


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Outside Diameter (O.D.) - Measure from rim to rim. Simply catch the hook of your tape measure on the rim, pull tight, and measure 180º directly across to the outisde edge of the opposite rim.

Bolt Hole to Bolt Hole - Most clamp rings will have either 3, 4, or 5 bolt holes (OMG, UFlow clamp rings have 6 bolt holes). Ensure that your measurement(s) are from the center of one bolt hole to the center of the next bolt hole. For each size clamp ring you will need the following measurements:

- 3 Bolt Hole Ring=120º
- 4 Bolt Hole Ring=180º & 90º
- 5 Bolt Hole Ring=72º


Outside Diameter (O.D.) - Turn the dome upside down and catch the edge of your tape measure on the dome's outside edge. Measure 180º across to the opposite outside edge. If there are locking tabs on your dome, do not include them in your measurement.

Height - From a flat surface, simply measure from the base of the dome to the highest point. Do not include any standoff tabs on the bottom of the dome.