Floor pump blowing wet air? I have a Lezyne Sports Drive floor pump.  It has worked fine for a couple of years, and it lives in my garage.  The handle is stored in the down position, so the cylinder is mostly empty.  The pump sits on the concrete floor.

 Mine has an older style of chuck on it though.

Today I went to use it while patching a road tyre, and pushing the handle was hard, and there was no air entering tube till the gauge hit 80psi.  The tube was not at 80psi - it was naked and maybe held 5-10psi.

I checked the schrader/presta adapter/pressure release thinking something was stuck in it, but that's just a threadded tube and was clear.

So I checked with the hose nozzle in my and it blew air with no resistance.   BUT it was very cold and my hand got damp.  Imagine a wet sneeze, but cold.

Aiming the hose at a clean dry surface, I gave it a pump and there's moisture visible.   30-40 pumps later the moisture is much reduced.

Questions


Does my pump have water in it?  
How did water get in there?
How do I get it out?
Yes, floor pumps can condense water in them. The water is from atmospheric water vapor. When the pump walls are colder than the surrounding air, the vapor can condense just like dew forms on leaves in the morning. Temperature swings assist in the formation of dew and this is made worse by leaving it on concrete, which is not only often much colder than the surrounding air, but also retains moisture.

After a while, the moisture in the pump will build up to the point where it has to get blown out the next time you use it. Especially, pumps like the Lezyne (which I also have) which are single-action designs, the top of the pump is open to atmospheric air and so the moisture can easily condense on the inner walls above the piston and trickle down into the main chamber.

How to get rid of it: 

1) Easy way: Dry pump a few times (i.e., pump it a few times with nothing attached) until nothing comes out. If you can do this outside in the sun, even better.

2) Slightly harder way: Do #1 first, then disassemble the top of the pump so that it's open to air. Take the piston out. Let everything air dry or dry on top of a radiator. While you have it apart, grease the piston seal slightly with the vendor approved lubricant -- usually any light silicon grease that is safe for teflon/rubber/leather.

How to prevent it from happening

Don't store your pump in a basement or garage where there is cool/damp air. Keep the pump off concrete. Store it somewhere where there is cool/dry air (best) or warm/dry air (second best). 

If that's not an option, you could also hang the pump upside down (with the handle in the stored configuration) so that any condensate that forms in the piston or on the handle will drip down. Keeping it away from the concrete floor would be an added bonus.

Bonus

Finally, here's a youtube video made by Lezyne showing how to overhaul their pump: