Preventive maintenance planning, asset priority, work orders, and documentation
Key Takeaways
- A preventive maintenance program schedules high-risk sewer segments before failures, using blockage history, FOG sources, roots, flat grades, surcharge complaints, and critical customers to set frequency.
- Work orders should capture location, asset ID, crew, equipment, cleaning method, debris removed, defects observed, photos or CCTV links, and the follow-up decision.
- CMOM means Capacity, Management, Operation, and Maintenance; exam scenarios usually test whether the utility is preventing SSOs instead of reacting after backups.
- A line that repeatedly needs emergency cleaning should be moved into a higher-frequency route, inspected by CCTV, and evaluated for source control or rehabilitation.
- The collection exam (Water Professionals International, formerly the Association of Boards of Certification) is about 100 scored multiple-choice questions with a 70% passing score; legal certification rules are set by each state or province.
Preventive maintenance as an SSO prevention system
A wastewater collection system maintenance program should be built around risk, not habit. The collection exam from Water Professionals International (WPI, formerly the Association of Boards of Certification, or ABC) is roughly 100 scored multiple-choice questions with a 70% passing score, and its outline includes high-pressure cleaning, inspection, emergency bypass operations, asset management updates, system-failure response, data collection, geographic information system (GIS) updates, and work planning.
The Environmental Protection Agency (EPA) Capacity, Management, Operation, and Maintenance (CMOM) framework points the same way: know your system, maintain it, document it, and use the records to prevent sanitary sewer overflows (SSOs).
Preventive maintenance (PM) means scheduled work done before a failure. In a collection system, PM includes cleaning known trouble spots, inspecting manholes, exercising and lubricating valves, checking air-release valves on force mains, verifying access, trimming vegetation off easements, calibrating flow meters, and updating maps. It is the opposite of emergency response after a basement backup, where the utility is already losing the SSO-prevention argument.
How to prioritize assets
The best exam answer links probability of failure with consequence of failure. A common field practice is a simple risk score, for example Risk = Likelihood (1-5) x Consequence (1-5), which produces a 1-25 ranking that sorts the cleaning and inspection schedule.
| Priority factor | What it suggests | Typical action |
|---|---|---|
| Repeated stoppages | Root intrusion, FOG, sag, offset joint, debris source, or poor grade | Increase cleaning frequency and schedule CCTV |
| Wet-weather SSOs | Inflow and infiltration or inadequate capacity | Flow monitoring, smoke testing, dye testing, CCTV, hydraulic review |
| Critical location | Hospital, school, highway crossing, or waterway | Higher inspection priority and a stronger emergency plan |
| Poor access | Buried or paved-over manhole, easement conflict, traffic hazard | Correct access before an emergency occurs |
| Age/material risk | Vitrified clay joints, brick manholes, corroded concrete, failing force main | Condition assessment and capital planning |
| Pump-station dependence | No gravity alternate route or single force main | Generator, bypass connection, spare pump, valve exercise |
Worked example: turning history into a schedule
Suppose a 600-foot, 8-inch clay main near a restaurant block has two grease stoppages in six months on a 12-month cleaning cycle. The mean time between blockages is about 3 months, well below the 12-month interval. The PM response is to shorten the interval to roughly half the failure spacing (so 6 weeks to 3 months), launch FOG source control, and queue CCTV. If a different 15-inch line has been jetted three times with almost no debris recovered and a clean CCTV run, the data supports extending its interval to recover crew hours for higher-risk segments.
Work orders that actually help operators
A useful work order does more than prove a crew was busy; it creates the next decision. Record the upstream and downstream manhole IDs, pipe size and material, cleaning direction, nozzle or tool used, water pressure and flow if relevant, volume and type of debris removed, unusual odors, surcharge evidence, customer contact, traffic control, confined-space notes, photos, and whether CCTV or repair is needed.
- Asset IDs and direction so the next crew finds the exact segment
- Method, tool, pressure, and footage cleaned
- Debris quantity and type (grease, grit, roots, rags, rock)
- Defects observed and a CCTV or repair recommendation
- Safety items: traffic control, confined-space entry, gas-monitor readings
Good records change routes. If a 12-month interval still produces grease plugs, move the segment to 3 or 6 months while source control proceeds. If the same line is cleaned monthly for roots, the durable answer is root control, joint repair, lining, or replacement, not endless rodding.
Exam traps
Do not pick answers that clean only after complaints, ignore wet-weather patterns, or keep cleaning the same line forever without finding the cause. Also avoid answers implying WPI issues one national license: WPI standardized exams support many programs, but legal certification, class level, and reporting duties come from the applicable state, province, or certifying authority.
Documentation, metrics, and the maintenance loop
The value of PM lives in the records. A mature program tracks measurable indicators so it can defend its budget and prove SSO prevention. Common metrics include feet of pipe cleaned per year as a percentage of the system (many utilities target cleaning a defined share annually, often a third or more on a multi-year rotating cycle), the number of stoppages per 100 miles of pipe, SSOs per 100 miles, repeat-failure locations, and the ratio of planned to reactive work hours. A program drifting toward mostly reactive hours is losing control of its system.
These records feed a continuous loop: collect field data, update GIS and the computerized maintenance management system (CMMS), re-rank risk, adjust cleaning frequency, schedule CCTV, and roll high-grade structural findings into the capital plan. The exam rewards answers that close this loop. When a scenario describes an operator who jets a line, restores flow, and goes home without logging debris type or recommending follow-up, that is the wrong answer even though service was restored, because the system learned nothing and the failure will repeat.
The right answer almost always documents the condition, identifies the cause, changes the schedule or triggers rehabilitation, and updates the records that drive the next decision.
A gravity main near several restaurants has caused two dry-weather backups in six months. Crews jetted the line both times and removed heavy grease. What is the best preventive maintenance response?
Which items belong in a useful sewer cleaning work order? Select all that apply.
Select all that apply
Which statement best matches the CMOM mindset for collection system maintenance?