Distinguish runoff from a soaked root ball
Fast runoff can occur while parts of a dry root ball remain poorly wetted. It can also be normal for an open medium. Check the container's weight and moisture within the root zone before deciding which situation applies.
When watering is appropriate, apply water evenly and let surplus drain. Do not respond to runoff by leaving the pot submerged indefinitely. If the medium is failing or roots are damaged, address that condition at a suitable repotting rather than endlessly repeating small splashes.
FAQ
Does quick drainage prove the roots received enough water?
No. Inspect the root ball rather than judging only by water leaving the hole.
Source
RHS: Growing houseplant cacti and succulents
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