I just watched this video... and have a question as a result


Based on what you see in the video, no matter the type of debris you vacuum -- isn't the filter basically useless if you always use a bag?

2 Answers 2


The filter is going to provide a means for the bag to not get sucked into the vacuum motor inlet. I have nearly the same machine as shown in the video and when the filter is removed, there is enough open space that the bag would block the inlet. One might think that should not matter, as the bag is porous, but what will happen is that small diameter opening will collect all the debris, quickly clogging the machine.

A very effective alternative to clogged filters and consumable vacuum bags is a cyclone-type chamber prior to the vacuum. There are disadvantages to having a second assembly, of course, but it creates a separation suitable to keeping the filter clean.

  • That makes sense. You're saying the vacuum is powerful enough to suck the bag into the intake port and potentially harm the motor etc. I don't intend to not use the filter, my new shop vac came with a filter and collection bag. My bigger observation was that if I keep using a bag, it doesn't seem like the filter will get clogged. It seems this is great for the blower feature of a shop vac as well (Having a bag), without a bag you basically clog the filter material with whatever debris are in the tank when you use the blower port as opposed to no debris in there at all when you use a bag.
    – amalik
    Sep 26, 2016 at 9:17
  • Your answer made me think of something else. It's often said online to remove the filter when doing wet pickup. I can't help but think the intake port would suck in water into the motor if you do that. Maybe a filter meant for wet-pickup is a better solution.
    – amalik
    Sep 26, 2016 at 9:24
  • I can't recall my latest machine's solution to wet pickup, but the previous one had a ball in a cage. When the water would reach high enough to be a threat to the motor, the ball would get sucked into the intake and block all airflow, preventing water damage. I've used my current machine for water and the configuration escapes me.
    – fred_dot_u
    Sep 26, 2016 at 10:07
  • Well Fred, I actually used my shop vac a lot today. Even with the bag on, it still catches a decent amount of dirt in the filter :)
    – amalik
    Sep 27, 2016 at 5:49

The bag will stop most of the debris, but there's always a chance of a small leak on the connection between the hose and the bag. Then the filter comes in handy.

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