If your air tanks do not have an automatic drain, when should you drain the air tanks?

• A. Every hour
• B. When the warning light comes on
• C. After every working day
• D. At the end of the week

Answer: (C)

Moisture forms in air tanks when air is compressed, so you must remove that water to keep the braking system clean and functioning. If there’s no automatic drain, draining at the end of each day (after you’ve finished driving) is the standard practice. This daily drain prevents water from building up, which can cause rust inside the tanks or freeze in cold weather and contaminate the air lines.

Draining every hour isn’t necessary and wastes time. Waiting for the warning light means letting water accumulate before you take action, which can be risky. Draining only at the end of the week allows too much moisture to collect. Doing it after each working day keeps the system dry and safer.