Which items must be checked on a 400-gallon water trailer before filling it?

The correct item to check on a 400-gallon water trailer before filling it is the interior, manhole, drain plug, and fill hose. This selection is crucial because these components directly affect the water quality and the safety of the water supply in the trailer.

Checking the interior ensures there are no contaminants present that could compromise the water. The manhole must be inspected to make sure it is properly sealed to prevent contamination when the trailer is filled. The drain plug is vital to verify that it is functioning correctly, as any leaks could lead to loss of water or, more importantly, the introduction of contaminants into the water supply. Lastly, the fill hose needs to be examined for any damage, blockages, or contamination to ensure that clean water is being transferred into the trailer without risk of introducing harmful substances.

While factors like battery and engine levels, tires, and light systems are important for the overall operation and safety of the trailer when transporting, they do not directly relate to the water storage and quality, which is the primary concern before filling the trailer with water. Similarly, examining paint condition and metal corrosion is vital for the long-term maintenance of the trailer but does not affect the immediate readiness for safely filling it with water.