Water operator math drill: 60 problems on the Formula/Conversion Table
WPI's standardized water treatment operator exams include calculation questions: 10% of the Class I and II exams, 12% of Class III and 15% of Class IV, shown in US standard units with metric units in parentheses. This drill is 60 original problems in 3 rounds of 20, on the constants and formulas of WPI's Formula/Conversion Table, in the full test player, with every step of every answer worked. Start with the 3 free problems.
- 60problems
- 3rounds
- 40min a round
- 3free
WPI's Need-to-Know Criteria state no time limit or passing score, so our 40 minutes a round (2 minutes a problem) is a pace, not a rule. Ask your certifying authority for your exam's rules. A practice score is a guide, not a prediction of your result.
The three rounds
Double-checked questions Real exam pattern Free sample · 3 problems
Operator Math Drill · Free sample
Free sampleInstant score, answer review and weak-topic diagnosis
Operator Math Drill · Round 1
Instant score, answer review and weak-topic diagnosis
Operator Math Drill · Round 2
Instant score, answer review and weak-topic diagnosis
Operator Math Drill · Round 3
Instant score, answer review and weak-topic diagnosis
What the problems cover
- Areas and volumes of circles, tanks, basins, pipes and cones
- Flow, velocity and detention time
- Chemical feed and dosage: lb/day, purity, hypochlorite, fluoride and pump settings
- Solutions, dilution and blending
- Filtration: loading rate, backwash rise rate and drop tests
- Pumping, pressure and horsepower
- Laboratory calculations: alkalinity, hardness, temperature, solids, odor and the Langelier index
- Basin loading: surface overflow, weir overflow, percent removal and pounds per day
- Unit conversions between gpm, MGD, cfs, acre-feet, pounds and kilograms, feet and meters
- Disinfection: chlorine demand and residual, CT and baffling factors
Every round has the same mix of the ten skills. Problems are in US units, with a few in metric. Every key and every wrong option is computed by script from the constants of the WPI Formula/Conversion Table (2024), and each wrong option illustrates a possible calculation error, named in the explanation.
Which exam applies to you
Each certifying authority chooses which exams it gives, and not every program uses WPI's standardized exams. This math drill follows WPI's Need-to-Know Criteria; ask your certifying authority which exam, classes and rules apply to you. Our water treatment operator exam guide sets out what WPI's Class I to IV exams cover and the exam-day rules WPI publishes.
Before you buy
What do I get?
60 problems in 3 rounds of 20, run in the full test player with a 40-minute clock per round. When you submit, you see your score by skill and, for every problem, the steps of the working and the slip behind each wrong option. Retake a round as often as you like.
Are these real WPI exam questions?
No. Every question here is original, written by us to the content areas WPI publishes. WPI's exam questions are WPI's copyright, and we do not claim to have any.
How were the answers checked?
Every key and every wrong option is computed by script from the constants in WPI's Formula/Conversion Table, and every problem was then solved again, independently and without our answer key, by reviewers. A problem went in only when their answers matched ours and nobody raised an objection to it.
Is this the current format?
WPI says calculation items are 10% of the Class I and II exams, 12% of Class III and 15% of Class IV. The formulas and constants are from WPI's 2024 table. Last checked 23 October 2026. Your certifying authority decides which exam you sit, so check with it before your test day.
Is it official?
No. This is independent practice by ProSyllabus, not produced, endorsed or checked by Water Professionals International or by any state certifying authority.
How do I pay and get access?
One payment by card (or PayPal where offered), handled by our payment provider. In the United States the price is charged in US dollars; in other countries in your own currency where we support it, otherwise in Indian rupees with the local figure shown as an estimate. Access opens on this device straight after payment. Sign in afterwards to keep it on your account. Purchase policy.
More water operator practice
- Class I Practice exam100 questions, 120-minute clock
- Class II Practice exam100 questions, 120-minute clock
Independent practice material. Not written or endorsed by Water Professionals International (WPI) or by any state certifying authority. These are original questions, not WPI exam questions. The format is stated as WPI's published Need-to-Know Criteria gave it on 23 October 2026; WPI's current documents and your certifying authority are the authority.