Here is the filter I used, for example,...

#4369K31 Corrosion-Resistant Air-Intake Filter, 1/4 NPT Male, 10 scfm @ 100 PSI Maximum Flow Rate

https://www.mcmaster.com/4369k31/

It comes with the filter element, but I also bought a spare...

#4369K38 2-1/4" High Paper Element for Corrosion-Resistant Air-Intake Filter

https://www.mcmaster.com/4369K38/

That was 4 years ago and the spare is still on the shelf. I take the filter out every year and blow it out (blowing from the inside outward). I check the condition of the filter by running the pump without it, note the pressure gage reading, then compare that to the pump running with it. When it was new, the pressure reading difference was barely noticeable on the gage. I will replace the filter when it shows a 1/2 psi or more.

Side Note, along with everything else...the filter assemblies have gone from $16 to $20 while the replacement filter has jumped from $2.50 to $3.13 (in the last 4 years). There are cheaper places to get your filters besides McMaster Carr. Their prices are typically higher than others since they cater to convenience.

A DIY prefilter that Bill mentioned is a nice addition. The pressure difference method to check the filters ability to pass air can be applied to the DIY system too whether it's for designing the prefilter or checking for a clogged filter.


Fish on!,
Noel