1. Oil and water usually collect in compressed air tanks. If you do not have an automatic tank drain, when should you drain the air tanks?
Detailed Explanation
Drain the tanks at the end of each working day when they do not have automatic drains. Compressed air can carry oil and water into the reservoirs; removing that moisture helps prevent corrosion and freezing. Draining only weekly or every four hours is not the routine interval this rule requires.
Correct Answer: After every working day.
Why This Matters on the CDL Test
This question belongs in your brake safety review. Pay close attention to pressure limits, inspection steps, stopping distance, and warning signs because brake-system mistakes are a common reason CDL applicants miss endorsement questions.
How to Remember It
Say the rule in your own words, then explain why the wrong answers are unsafe or incomplete. That habit makes similar Air Brakes questions easier when the exam changes the wording.
Answer Review
Choose "After every working day." because this answer matches the safe CDL action for brake system safety. On the knowledge test, the safest answer is usually the one that protects space, control, visibility, legal compliance, or inspection accuracy before the vehicle is put at risk.
Why the other answers are weaker
- After every four hours of service."After every four hours of service." does not best answer this brake system safety question. When you see a similar option on the CDL permit test, compare it against the exact safety rule and choose the answer that prevents the most immediate risk.
- Once a week."Once a week." does not best answer this brake system safety question. When you see a similar option on the CDL permit test, compare it against the exact safety rule and choose the answer that prevents the most immediate risk.
Test-Day Checklist
- Read the question once for the topic, then read it again for the exact CDL action being tested in Air Brakes.
- Eliminate answers that sound convenient but skip an inspection, warning sign, or safety step.
- Say the correct rule out loud before moving on so you can recognize it when the exam changes the wording.
Study the Full Topic
Review what the air pressure gauge tells you, how low-pressure warnings work, and why air tank checks matter.
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Start Practice TestRelated Questions
64. If you do not have automatic tank drains, how often should you drain the oil and water from the bottom of compressed air storage tanks?
2. Why should you drain water from the compressed air tanks?
54. The storage tanks are used to hold compressed air.
68. If oil and water collects in the air tanks what can happen to the brakes?
If using air tanks with manually operated drains, how often should you drain the tanks?
Keep Studying Air Brakes
Question pages help you review one rule at a time. To build test-day speed, move back into the full Air Brakes practice test and answer a mixed set without looking at the explanation first.
State CDL Practice Paths
After you understand this answer, use a state practice path to connect the federal CDL rule with the DMV test pages drivers search for most.