NPLQ Pool Equipment and Maintenance 2 — Questions and Answers
Question 1: What is the function of the pool's main circulation pump in relation to water quality?
- To heat the pool water only
- To circulate water through the filtration and chemical dosing system, maintaining water clarity and chemical distribution (Correct answer)
- To fill the pool from the mains supply
- To remove water during pool closures
Correct answer: To circulate water through the filtration and chemical dosing system, maintaining water clarity and chemical distribution
The circulation pump drives pool water through the filter and dosing system, ensuring constant water treatment and even chemical distribution throughout the pool.
The pool circulation system consists of the main pump, strainers, filters, chemical dosing points, and return inlets. The pump draws water from the pool via surface skimmers and main drains, passes it through the filter, and returns it to the pool. Chemical dosing occurs in the circulation pipe after filtration. Circulation rate is measured as turnover period — UK guidance recommends 2–4 hours for leisure pools.
Question 2: What should a lifeguard do if they find a pool rescue tube is cracked and partially deflated?
- Continue using it carefully until replaced
- Remove it from service immediately, report it to the duty manager, and ensure a replacement is available before the pool opens (Correct answer)
- Inflate it with a pump and continue using it
- Report it at the end of the shift
Correct answer: Remove it from service immediately, report it to the duty manager, and ensure a replacement is available before the pool opens
Defective rescue equipment must be taken out of service immediately. A cracked, deflating rescue tube cannot be relied upon in an emergency and creates life-safety risk.
Rescue tubes are primary safety equipment and must be inspected before every operational period. Defects — including cracks, foam degradation, worn straps, or broken clips — must be reported immediately and the item removed from service. Pool operating procedures should include a pre-shift equipment checklist covering all safety equipment.
Question 3: What is the purpose of backwashing a sand filter in a pool's filtration system?
- To add fresh chlorine to the filter media
- To reverse the water flow through the filter to flush out accumulated debris and restore filtration efficiency (Correct answer)
- To test the filter's flow rate
- To add fresh filter sand
Correct answer: To reverse the water flow through the filter to flush out accumulated debris and restore filtration efficiency
Backwashing reverses water flow through the filter, dislodging trapped particles and debris which are then flushed to waste, restoring the filter's effectiveness.
Sand filters collect suspended particles as pool water passes through the filter bed. Over time, the bed becomes clogged and filter pressure rises, reducing flow rate and water clarity. Backwashing reverses the water flow, expanding the sand bed and flushing trapped material to the waste drain. Backwashing is typically triggered when the pressure differential rises by 0.5 bar above the clean-filter baseline.
Question 4: What are the recommended pH range and free chlorine residual for a public indoor swimming pool?
- pH 6.5–7.0, chlorine 0.5–1.0 mg/l
- pH 7.2–7.8, free chlorine 1–3 mg/l (Correct answer)
- pH 8.0–8.5, chlorine 4–6 mg/l
- pH 7.0, chlorine 10 mg/l
Correct answer: pH 7.2–7.8, free chlorine 1–3 mg/l
UK guidance (PWTAG) recommends pH 7.2–7.8 and free chlorine residual of 1–3 mg/l for public indoor pools, balancing disinfection effectiveness with bather comfort.
Chlorine's disinfection effectiveness is highly pH-dependent. At pH 7.2, approximately 67% of chlorine exists as the active hypochlorous acid form; at pH 7.8, this falls to around 33%. This is why maintaining pH below 7.8 maximises disinfection. PWTAG recommends: pH 7.2–7.8 (target 7.4), free chlorine 1–3 mg/l. Tests should be taken at least every 2 hours during operation.
Question 5: What is a 'combined chlorine' reading and what does a high value indicate?
- The total of chlorine from two dosing pumps
- Chloramines formed when chlorine reacts with bather pollution — a high level indicates insufficient disinfection and causes 'pool smell' and eye irritation (Correct answer)
- The chlorine concentration in both the deep and shallow ends
- The sum of chlorine added over 24 hours
Correct answer: Chloramines formed when chlorine reacts with bather pollution — a high level indicates insufficient disinfection and causes 'pool smell' and eye irritation
Combined chlorine (chloramines) forms when free chlorine reacts with ammonia from bather waste. High levels cause the characteristic 'pool smell', eye/skin irritation, and indicate inadequate free chlorine relative to bather load.
Chloramines are poor disinfectants and cause respiratory irritation, eye redness, and the characteristic 'pool smell' often mistakenly attributed to too much chlorine. The opposite is true — the smell means there is not enough free chlorine to break down the chloramines. PWTAG recommends combined chlorine should not exceed 1 mg/l. High combined chlorine is addressed by: increasing free chlorine, improving bather hygiene, and superchlorination or UV supplementary disinfection.
Question 6: What is the lifeguard's responsibility if they smell a strong chemical odour (such as chlorine gas) in the pool plant room?
- Enter and investigate the source of the odour
- Evacuate the area immediately, raise the alarm, do not re-enter, and call emergency services (Correct answer)
- Open the plant room windows and continue working
- Increase ventilation and report to management at the end of the shift
Correct answer: Evacuate the area immediately, raise the alarm, do not re-enter, and call emergency services
Chlorine gas is a highly toxic respiratory irritant. Any strong chemical odour from the plant room requires immediate evacuation and emergency services — do not re-enter without breathing apparatus.
Chlorine gas is 2.5 times denser than air, accumulates at floor level, and is lethal at high concentrations. Actions: evacuate all personnel immediately, do not attempt to investigate without SCBA, call 999 (fire brigade with HazMat capability), assemble at the designated muster point, and keep the public away. The pool must be closed until the HSE clears it.
NPLQ Pool Equipment and Maintenance 2
What is the function of the pool's main circulation pump in relation to water quality?