Kobalt Oil-free Compressor spits water

Yes, you can and should put a moisture trap/line filter on those, but those only protect your discharge lines. Even more important is the drain plug on the bottom of the tank! Airborne moisture/condensation builds up in these tanks VERY quickly (especially this time of year) and can rot out your tank fairly quickly if you don't drain them often. I've seen new tanks come with just a pipe plug in them; pull that out and put a decent valve on there and use it regularly (I do it every week or two) to keep your tank dry. You'd be shocked to see how much water comes out of there!