What it means
Waterfall enrichment looks for a data point across several providers in turn, stopping at the first one that returns a good result. If the first provider has no verified email for a contact, the request falls to the second, then the third.
Each provider covers different people well, so a waterfall finds more of what you need than any single source. Each step also needs a quality bar: a waterfall that takes the first answer, verified or not, fills fields with guesses. Order matters. Put the cheapest check first, so the paid steps only ever see the leftovers.
How we use it
We run waterfalls for finding contacts and for verifying them. When an address fails verification, the Email Verification Waterfall tries four finders in sequence and verifies each candidate by the same rule.
Sourcing follows the same logic. The Lead Sourcing Waterfall builds one list, sourced cheapest first, with a cost gate before anything is spent. Keeping the paid steps for the leftovers keeps the cost per verified contact down.