Measure at the right height
To determine the diameter of your downpipe, measure approximately at the height at which the rainwater filter is to be installed. In this way, you avoid determining an incorrect value for slightly conical downpipes.
Determine with the correct diameter
The diameter can be determined directly with the caliper gauge or, more colloquially, the slide gauge. When measuring, rotate slightly around the downpipe to determine a suitable average value.
Measuring the circumference with the tape measure
Use the tape measure to determine the circumference of the downpipe. The diameter can also be derived sufficiently well from this by dividing the value by 3.14.
Relationship between circumference and diameter
As an example, these circumferences result in approximately the following downpipe diameters: