Shop Vac, secondary filter material?

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Established Member
14 May 2022
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I want to use a secondary filter material to save my filter on my Shop Vac. Like the material that is used in the smaller vacs, when bags will take up too much of the already limited space in a little drum. These tend to be placed over the top of the drum/bin section and then the top/lid/filter section is lowered into place and clamped down as per normal. The seal/clamp for the filter material being where the bin and lid meet.

Anyway, what is this material called?... so I can look up and research it's different grades, thicknesses', etc...

Thanks... I hope I have explained this well.
I have no idea what it’s called but I know what you mean. Depends on the size of of your vac b but I have a numatic nv750 that has a large secondary filter that’s fit’s exactly as you describe . Maybe look at purchasing that or one similar that could fit your vac. I’ll try to find a link ..
Thanks, this is something for me to look into.(y)

I was thinking of more just a piece of flat fabric, without any plastic ribbing or stitching. I will cut the fabric to length/width.
I think it's on an Axminster site where they recommend cutting open a filter bag and putting it over the top of the drum between the drum and motor housing to provide secondary filtering.
As @MikeJhn says above, a cut open bag is a good way to do this as recommended by Numatic. The Axminster NVD750 is a Numatic in Axminster colours so they are just repeating the manufacturers advice.

I use Numatic HEPA bags myself, cut at the seams and then circles cut out to fit my Nilfisk commercial vac. It's a cheap way to upgrade it with a third filter.