PADI Equipment Knowledge & Maintenance 3 — Questions and Answers
Question 1: What is the correct procedure for rinsing a regulator after a saltwater dive?
- Soak and rinse with fresh water without pressing the purge button, keeping the dust cap in place (Correct answer)
- Rinse under high-pressure fresh water while pressing the purge button
- Use mild soap solution and rinse in salt water to preserve O-rings
- Allow it to air dry in sunlight before any rinsing
Correct answer: Soak and rinse with fresh water without pressing the purge button, keeping the dust cap in place
The dust cap must be in place and the purge button must NOT be pressed during rinsing to prevent water from entering the first stage.
Question 2: A diver notices their SPG reads lower than expected at the start of a dive. What is the most likely explanation?
- The cylinder was not fully filled or gas was lost from a leaking valve (Correct answer)
- The SPG gauge is calibrated in bar instead of PSI
- Cold water contracts the gauge Bourdon tube reading
- The regulator first stage is restricting gas flow to the SPG
Correct answer: The cylinder was not fully filled or gas was lost from a leaking valve
An unexpectedly low SPG reading at dive start almost always indicates the cylinder was not topped off or gas escaped through a leak.
Question 3: Why are aluminum scuba cylinders anodized on the exterior?
- Anodizing creates a hard oxide layer that resists corrosion and surface abrasion (Correct answer)
- Anodizing adds structural strength to offset aluminum's lower tensile strength
- Anodizing color-codes cylinders for specific gas mixtures
- Anodizing prevents electrolytic reaction between the valve and cylinder neck
Correct answer: Anodizing creates a hard oxide layer that resists corrosion and surface abrasion
Anodizing converts the outer aluminum surface into aluminum oxide, which is harder and far more corrosion-resistant than bare aluminum.
Question 4: Which component in a BCD oral inflator allows the diver to add air by mouth without it escaping back out?
- A one-way check valve inside the mouthpiece assembly (Correct answer)
- A pressure-relief valve set below oral inflation pressure
- The corrugated hose itself, which compresses to seal
- A rubber flap on the BCD bladder inlet
Correct answer: A one-way check valve inside the mouthpiece assembly
The one-way check valve allows air to enter the bladder from the mouthpiece but prevents it from flowing back out during exhalation.
Question 5: What is the purpose of a drysuit's non-return valve (inflator valve)?
- It allows gas to enter the suit for thermal insulation and prevents backflow into the cylinder hose (Correct answer)
- It vents excess gas automatically when the suit overpressurizes
- It seals the suit inflator port when not in use to prevent leaks
- It regulates the flow rate of gas into the suit during descent
Correct answer: It allows gas to enter the suit for thermal insulation and prevents backflow into the cylinder hose
The non-return (check) valve on a drysuit inflator port allows gas from the cylinder to enter the suit but blocks backflow toward the regulator.
Question 6: What is the recommended maximum fill pressure for a standard aluminum 80 scuba cylinder rated at 3000 psi?
- 3000 psi (207 bar) — the rated working pressure (Correct answer)
- 3300 psi (228 bar) — ten percent overfill is standard practice
- 2640 psi (182 bar) — cylinders should be filled to 88% to prolong life
- 3500 psi (241 bar) — extra fill compensates for surface temperature
Correct answer: 3000 psi (207 bar) — the rated working pressure
Aluminum cylinders should be filled only to their rated working pressure — in this case 3000 psi — to avoid stress beyond design limits.
Question 7: Which of the following best describes the function of a tank boot on a scuba cylinder?
- Protects the cylinder base from impact and provides a flat surface for standing the tank upright (Correct answer)
- Increases buoyancy of the cylinder at the surface
- Prevents corrosion of the cylinder bottom when stored in water
- Locks the cylinder into the BCD backplate carrier
Correct answer: Protects the cylinder base from impact and provides a flat surface for standing the tank upright
A tank boot cushions the base of the cylinder from impact damage and gives it a stable, flat surface to stand on.
PADI Equipment Knowledge & Maintenance 3
What is the correct procedure for rinsing a regulator after a saltwater dive?