‘Based on Available Data’: The Four Words That Should Make Engineers Nervous

“Based on available data” is working harder in your spec than four words should.

It shows up in EPC documentation constantly, and it’s technically accurate every time — the data you had was the data you used. That’s also the problem. The phrase is a hedge, not a finding. It tells the reader the design basis reflects whatever characterization window happened to be available, not the conditions the system will face over its actual life.

Conservative sizing. Self-cleaning capable. Low maintenance. Based on available data. The filtration industry has built a whole vocabulary that sounds like a claim while functioning as a liability shield. None of these phrases are false, exactly. They hold up in a design review and fall apart the first time total suspended solids (TSS) spikes past whatever the available data suggested it would.

A phrase like this belongs in a project document only when the engineering underneath it is solid enough to say something more specific. If a system genuinely performs at TSS loads above the characterization average, say that, and show the data behind it. If it doesn’t, “based on available data” is doing the work of concealing that gap — and everyone downstream inherits it. The operator overriding the system at 2 a.m. The engineer who gets the callback a year later.

Ask the question the hedge is avoiding: what’s the highest TSS this application will actually see, and does the system hold performance there without someone standing next to it? If the vendor’s answer is another version of “based on available data,” you have your answer.

Most vendors you evaluate will use some version of that phrase. What’s worth finding out is which vendors can replace it with something more specific, and which ones are hoping you won’t ask.