Q. How do I determine whether a container is airtight?

Answer

If someone is able to pump air into the container for an indefinitely long period (with something like a bike tire pump for example) then the container does not have an airtight seal. If it becomes increasingly challenging the container most likely does not allow air in (up to a certain pressure at which the sealing breaks). The drum is to be utilized while lying on its side and having around two thirds of its capacity filled with liquid. Because of this any leaking at the drain will be instantly noticeable to the eye. The same rule applies to the pipe that water enters therefore that part of the system must also be flooded with water.