Waterfall Enrichment
By Federico Donatone · Updated October 15, 2026Waterfall enrichment is a method for filling missing contact or company data by querying several data providers in sequence. The first provider runs on every record, and each next provider runs only on the records still missing a valid result. The goal is higher coverage than any single database, at the lowest cost per usable record.
How waterfall enrichment works
Think of a bucket brigade. You start with a partial record, usually a person's name and a company domain, and you need one field, such as a verified work email. Provider A gets the first try. If it returns an address that passes verification, the waterfall stops for that row and saves the source. If it returns nothing, or an address that fails, the row drops to provider B, then C, until the field is filled or the providers run out.
- Write the field contract: which fields you need and what counts as an acceptable result. For emails, that means valid in an outside verifier, not catch-all (a catch-all domain accepts mail for any address, so nobody can confirm the person exists).
- Remove duplicates, current customers and excluded accounts before any paid lookup.
- Run the first provider on every remaining row.
- Send only the misses to the next provider, and repeat.
- Verify every result, save its source and date, and send empty rows to manual research or out of the campaign.
Why one data provider is not enough
No database covers every market, job title and company size. When Growth Cab ran the same 600 leads through 8 contact data providers and verified every email, the best single result was Apollo, with verified emails for 68.0% of the leads. The lowest was Icypeas at 27.2%. Even the leader left roughly one lead in three without a verified address.
Reach is only half the story. The same Growth Cab test counted dead emails that providers had labeled valid: 63 for RocketReach, 49 for Lusha, 24 for Apollo and 1 for Prospeo. Mobile numbers varied too: on a 50-lead sample, Prospeo found 35, Apollo 34 and LeadMagic 19. A waterfall needs its own verification step, because trusting each vendor's valid label passes their errors straight into your bounce rate. The full results are in our test of 8 lead generation databases.
How to order providers in a waterfall
Provider order is a cost decision as much as a coverage decision. The first provider runs on every row, so it should be the one with the best price per verified result on your market. Later steps only see the hard rows.
| Ordering rule | Why it matters |
|---|---|
| Cheapest accurate source first | Most rows get filled at the lowest price |
| Precise valid labels early | Fewer dead emails reach your sequences |
| Specialists last | Mobile or regional sources pay off on hard rows |
| Retest the order every quarter | Coverage shifts as databases change |
Waterfall enrichment tools and cost
Clay is the best-known tool built around this method: each column can call a different provider and run only when the column before it came back empty. Some all-in-one prospecting platforms run a waterfall inside the product, and a developer can script one against provider APIs.
Check billing rules before you estimate cost. Some providers charge for empty lookups, verification or retries. The number to track is cost per accepted record: total spend divided by the records that passed verification and entered a campaign. For a wider view of the tools, see our guide to B2B data enrichment tools.