I am just finishing the assembly of a vacuum chuck and I'm using an HVAC pump because I already have one. Thanks to some comments I've read here I'm wrapping the oil port with loosely woven material to filter oil mist. I need to tighten some fittings but right now I've got 25 in.Hg so I'm pleased. The Venturi I have struggled to get to 17 in.Hg plus of course that meant relying on my very loud compressor.

I've read that some people install an inline automotive fuel filter. Am I right in assuming that this serves to filter air coming into the pump through the bleed valve?

Thanks, Richard