The Fault Predates Your Involvement (Decision Tree)

Why this matters

You arrive, and a condition that was there before you is now going to look like it is yours. A customer sees a crack, a leak, or a dead circuit and connects it to the last person who touched the system, which is you. Sometimes you find it yourself mid-job and know it did not start on your watch. Either way, the question is chronology: did this fault exist before you got involved. Getting the answer right, with evidence, protects you from eating a repair you did not cause and keeps you honest about the ones you did.

Safety comes before chronology

If the pre-existing fault is a live hazard, make it safe before you spend one second on who caused it. A gas smell means get people out and call the utility. An exposed or energized conductor means de-energize and verify dead. Backdrafting or a suspected combustion problem means shut the appliance down and check for carbon monoxide. Standing water near electrical means kill power first. The blame question can wait five minutes; the hazard cannot. Once the scene is safe, go back to the timeline.

Start here: read the fault's age

Before you talk to anyone, read the physical evidence. Old faults carry corrosion in the wound, dust cake over the break, oxidized edges, and secondary wear; fresh ones are bright, clean, and sharp (see the related recent-versus-pre-existing article for the full tells). The age of the evidence is your anchor, because it is not an opinion the customer can argue with.

If the evidence is clearly old - corroded, layered, worn - the fault predates recent events and almost certainly predates a visit you made days ago. Photograph it and move to communication.

If the evidence is fresh, do not assume you caused it; keep going, because a fresh break can sit on an old worn part.

Did you or your shop touch this system before

If you have never been to this system, the whole question is the fault's age against your arrival. A wear clock reading months or years, against a first visit measured in days, puts the fault before you. State the window, not a false-precise date.

If your shop has been here before, narrow it: did this exist at your last visit. Pull your own prior notes and photos. Your clean, dated work from last time is a reference surface; new corrosion or damage over it started after you left. If your records show the component was sound and to spec when you finished, that is your defense.

Could your work have been the last straw

A part that was already failing can let go when you cycle it, pressure-test it, restart it, or re-energize it. That makes you the trigger of the timing, not the cause of the fault.

If the part is heavily worn, corroded, or fatigued everywhere except a fresh final break, it was at end of life and reached it now. Document the pre-existing wear and explain the distinction plainly: normal, necessary work disturbed a part that was already spent.

If the part was sound everywhere except where your work damaged it, that is on you. Own it early; the same evidence that clears you when you are innocent convicts you when you are not.

The customer is blaming you

Lead with evidence, not defense. An argument is your word against theirs; a photo of corrosion inside the crack is neither.

1. Show the aged evidence and describe what it means in plain terms.
2. Give your honest read of the timeline, as a window: "this has been leaking slowly for months, well before we were here."
3. Do not raise your voice or your bill. Show, do not argue.
4. If the fault genuinely predates you and the customer still disputes it, your documentation is what a manager, an adjuster, or a warranty rep will rely on.

When you honestly cannot tell

Sometimes the evidence is ambiguous and you cannot support a confident chronology. Say so. Do not assert a timeline you cannot back, because a wrong confident claim is worse than an honest "I cannot date this precisely." Then decide who absorbs it deliberately, weighing the relationship against the truth, rather than defaulting to a fight or a giveaway.

The order to run it

1. Make any hazard safe first, before the blame question.
2. Read the fault's age from the physical evidence and photograph it.
3. Check whether you or your shop touched this system before, and pull prior records.
4. Separate triggering the timing from causing the fault.
5. If blamed, lead with evidence, not defensiveness.
6. If you cannot date it honestly, say so and decide deliberately.

References

• Trade-standard practice for failure attribution and field documentation
• OSHA general guidance on hazard control before non-urgent work
• Insurance-industry guidance on pre-existing condition versus new loss
• See related: Separating Recent Damage from Pre-Existing Wear; Reading Corrosion and Wear as a Clock; Is This Failure Your Fault or Normal Wear (decision tree)