What Is Waterfall Enrichment (and Why Single-Source Tools Miss Half Your Contacts)

I ran an enrichment test last month where one tool found emails for 76% of profiles and another found emails for 44%. Same 25 people. Same day. Same test.

The difference came down to how many data sources each tool checks.

The way most enrichment tools work

When you use an enrichment tool to find someone's email or phone number, here's what usually happens behind the scenes: the tool sends the person's name and company to a database, the database looks them up, and you get a result back. Either it has the data or it doesn't.

That database is built from web scraping, data partnerships, user-contributed contacts, business registries, and social media profiles. The provider collects all of this, cleans it, and makes it searchable.

The problem is that no single database has everyone.

Provider A might be strong on US tech companies because their data partnerships are with US-based sources. Provider B might have better European coverage because they've scraped more EU business directories. Provider C might specialize in phone numbers because they've acquired a telecom data company.

Each provider has blind spots. Different blind spots, but blind spots nonetheless.

When your enrichment tool queries one provider and that provider doesn't have the person you're looking for, you get an empty result. The tool tried. It failed. You move on without the email.

What waterfall enrichment does differently

Waterfall enrichment doesn't stop at one database. It queries multiple providers in sequence.

The process looks like this: the tool sends a request to Provider 1. If Provider 1 has a valid email, you get that email. If Provider 1 comes back empty, the tool automatically sends the same request to Provider 2. Then Provider 3. Then Provider 4. And so on, until either a provider returns a result or the tool runs out of sources to check.

It's called "waterfall" because the request cascades down through providers like water flowing over steps. Each step is a chance to find data that the previous step missed.

The math works in your favor. If Provider 1 has a 60% chance of finding a given email, and Provider 2 independently has a 55% chance, running both in sequence gives you roughly a 82% chance of finding it. Add a third provider at 50% and you're at 91%. The more sources you check, the higher your overall coverage, assuming the providers have genuinely different databases and not just resold copies of the same data.

Why the coverage gap is real

In an enrichment test I ran on 25 LinkedIn profiles, the tool querying 20+ providers found emails for 19 of them (76%). A tool relying primarily on its own database found 17 (68%). A tool with a smaller data pool found 11 (44%).

The eight-email gap between 19 and 11 is the waterfall effect. Those eight people existed in at least one of the additional databases the first tool checked. The third tool never got to those databases because it didn't have access to them.

Phone numbers showed an even bigger spread. The waterfall tool found phone numbers for 21 out of 25 profiles (84%). The smallest data pool found 8 (32%). That's a 52-percentage-point gap on the same set of people.

Geography made the difference more obvious. All three tools did well on US-based contacts at mid-size and large companies. Those are the easiest profiles to find data for. But when I tested contacts in the UK, or at smaller companies, or people who'd recently changed jobs, the single-source tools started returning empty results while the waterfall tool kept finding matches.

The contacts that waterfall enrichment helps you find are exactly the ones that are hardest to reach. They're the people who aren't in every database. If everyone already had their email, you wouldn't need the tool in the first place.

The tradeoffs

There are tradeoffs worth knowing about before you commit to a waterfall tool.

Speed. Querying one provider takes a second or two. Querying twenty providers in sequence can take 10-30 seconds, especially if the tool has to wait for each one to respond before trying the next. Some tools run providers in parallel to reduce this, but it's still slower than a single lookup.

Cost. Each provider charges for lookups. A waterfall tool checking 5-10 providers per contact has higher per-lookup costs than a tool checking one. That cost gets passed to you in the pricing. If waterfall tools are more expensive than single-source tools, this is usually why.

Data conflicts. Different providers sometimes return different emails for the same person. Provider 1 might return the person's current work email. Provider 2 might return the email from two jobs ago. The waterfall tool has to decide which one to trust. Most tools use recency signals and verification to pick the best result, but it's not always right. During my test, a couple of contacts got emails from a previous employer, probably because that was the most recent "verified" result in the provider chain.

Diminishing returns. Going from 1 provider to 5 is a big jump in coverage. Going from 15 to 20 providers adds much less. At some point, the providers you're adding have the same data as the ones you've already checked. The first few steps of the waterfall do most of the work.

How to tell if your tool uses waterfall enrichment

Most enrichment tools don't advertise their architecture clearly. Here are a few ways to figure out what's happening under the hood.

Check the pricing page. Tools with waterfall enrichment tend to be more expensive per credit or per lookup. If a tool charges $0.01 per email lookup and a competitor charges $0.10, the expensive one is probably checking more sources.

Ask directly. "How many data providers do you query for each lookup?" is a reasonable question for any vendor. If the answer is vague ("we have a comprehensive database"), they probably use one source. If the answer includes a specific number ("we query 15-20 providers"), that's a waterfall.

Run a side-by-side test. Take 20 profiles and run them through two tools. If one tool consistently finds data that the other misses, the one with higher coverage is likely checking more sources. This is the most reliable signal because it tests on your actual prospects, not on the vendor's cherry-picked demo data.

Look at the speed. If enrichment takes 15-30 seconds per contact, the tool is probably querying multiple sources. If it returns results in under 2 seconds, it's probably a single lookup.

When waterfall matters (and when it doesn't)

Waterfall enrichment matters most when your prospect list includes:

• People at small companies. Enrichment databases tend to have better coverage of large companies. If you're selling to startups or SMBs, single-source tools will miss more contacts.
• International contacts. US data is the easiest to find. European, Asian, and Latin American contacts are where single-source tools start falling short. If you prospect outside the US, test your tool on international profiles specifically.
• Recent job changers. When someone moves to a new company, it takes weeks or months for databases to update. A waterfall tool checking 15 providers is more likely to have at least one that's already updated.
• Niche industries. Tech and finance contacts are over-represented in most databases. If you sell to manufacturing, healthcare, construction, or government, single-source coverage drops and waterfall becomes more valuable.

Waterfall matters less when your prospect list is entirely US-based tech workers at well-known companies. In that scenario, most tools will have decent coverage and the marginal benefit of extra providers is small.

The question to ask yourself

If you're evaluating enrichment tools, the question isn't "which tool has the highest match rate on their website." It's "which tool has the highest match rate on my actual prospects."

The only way to answer that is to test. Pick 20-25 profiles from your real pipeline, sign up for free tiers, and run them through. Count not just whether data was found, but whether the data is usable. A wrong-country phone number counts as a miss. An email from a company the person left last year counts as a miss.

If you sell to one geography, one industry, and one company size, a single-source tool might cover you fine. If your prospect list is diverse, waterfall enrichment is probably worth the extra cost.