Preventive vs. Reactive Maintenance: Which Strategy Belongs Where?
"Preventive maintenance is always better than reactive maintenance" is one of those things every CMMS vendor will tell you and every honest maintenance veteran will roll their eyes at. The truth is that the right strategy depends on the asset. Preventive maintenance pays off enormously on critical, expensive, or hard-to-replace equipment, and it wastes labor when it is forced onto assets where reactive repair is cheaper.
The job of a maintenance program is not to maximize PMs. It is to allocate finite labor and parts dollars across hundreds of assets in a way that minimizes total cost and risk. Below is the framework most public works, utility, and facility teams converge on once they get past the early CMMS hype.
What "preventive" and "reactive" actually mean
- Reactive maintenance (run-to-failure). You fix it when it breaks. The cheapest strategy per task, the most expensive when consequences are large.
- Preventive maintenance (PM). Scheduled work performed at a fixed interval — time, meter, or cycles — to prevent failure. Cheap insurance on critical assets.
- Predictive maintenance (PdM). Condition-based — sensors, vibration, oil analysis, telemetry — trigger work only when an indicator crosses a threshold. The most efficient when the data is available; overkill when it is not.
The decision matrix
Plot every asset on two axes:
- Consequence of failure. What does it cost — financially, operationally, reputationally — if this asset goes down without warning?
- Cost of prevention. What does the PM cycle cost in labor, parts, and downtime?
From those two axes:
- High consequence, low prevention cost → aggressive PM. Lift station #3 going dark on a holiday weekend will cost more in one event than a year of quarterly inspections.
- High consequence, high prevention cost → predictive maintenance. Use sensors, telemetry, runtime data to trigger work only when needed. Investment in the data pays for itself.
- Low consequence, low prevention cost → light PM. Annual inspection is fine. Don't overdo it.
- Low consequence, high prevention cost → reactive. Run it until it fails. The light bulb in the storage room does not need a quarterly inspection.
Rule of thumb: if the cost of one unplanned failure exceeds the cost of a year of preventive checks, PM wins. If not, reactive is usually cheaper.
Where municipalities most often get it wrong
Two failure modes dominate.
Failure mode 1: PM theatre. Every asset gets the same quarterly check because that is what the spreadsheet says. Crews go through the motions, click "complete," and nothing meaningful is inspected. The KPI looks great. The infrastructure still fails.
Failure mode 2: full reactive. No PM at all. The team is heroic, but always behind. Overtime is the budget. Capital replacements come in waves because nothing is monitored until it dies.
The fix is the same in both cases: a real asset registry, with PM strategies set per class of asset, not per organization.
How a CMMS supports the mix
A modern CMMS should let you assign a different strategy to every asset class without making the supervisor write code. At minimum, it needs:
- Time-based PM. Every 30 / 90 / 180 / 365 days, with auto-generated work orders.
- Meter-based PM. Every 5,000 hours, every 10,000 miles, every 250 cycles.
- Condition-based triggers. Sensor crosses a threshold → work order opens.
- Asset class templates. Define the PM once for "lift station," apply it to all 18 of them, override per-asset where needed.
- PM compliance reporting. Show, by division, what was scheduled vs. completed vs. missed. This is the report your auditor wants.
Building a starter PM program
If you are starting from zero, do not try to PM every asset on day one. Instead:
- Pull the top 20 assets by replacement cost or by failure consequence.
- Set a baseline PM strategy for each from the manufacturer's recommendation.
- Run that program for one quarter. Track completion and failures.
- Add the next 20 assets. Adjust intervals based on what you saw in quarter one.
In a year, you will have a defensible PM program that covers 80% of the consequence-weighted asset value, without burning out crews on PMs that don't matter.
Where AI fits
AI is starting to play a real role in tuning PM intervals. By correlating completed work order history, parts usage, and downtime, an AI assistant can flag assets where the current PM interval looks too aggressive (no defects found in 12 cycles) or too lax (failures occurring before next scheduled PM). The supervisor still decides; the AI surfaces the candidates. More on AI in operations.
WorkmanIQ ships time-based, meter-based, and condition-based PM out of the box, with AI-suggested interval tuning. See how it works →