Some competitive filters come with manual drains. Unless you are disciplined in checking and draining your filter bowls, this is not a good idea. If filter bowls aren’t drained, water levels rise within the bowl and can contaminate the filter element that removes particulates, reducing its effectiveness and reducing air flow to your tools. Other filters come with “overnight drains” that automatically drain when the system is depressurized overnight. These work well if the system is truly depressurized, and if atmospheric humidity is low enough that the bowl wouldn’t fill excessively before overnight depressurization occurs. In high humidity conditions or if depressurization isn’t consistently done, they are no more effective than manual drains. This line of Milton filters will auto-drain throughout the day as the bowl begins to fill, performing effectively with little maintenance. They can also be manually drained as desired.
Many competitors use inexpensive filter elements to keep costs low, such as borosilicate or polyethylene. We use a bronze sintered filter element that provides long life, won’t deteriorate in humid operating conditions, and is washable.