make a manual vacuum pump for under $20 by converting a bicycle pump

Step 8 Attach the hose and the new check valve

Now cut a short piece of hose, about an inch or so long, and fit it over the hose barb. The piece of hose should be long enough to accommodate the barb, and the barbed end of a check valve, but not much longer. (Maybe a quarter of an inch extra.) Any extra space between the pump and the check valve will reduce the vacuum level you can pull, so don't use a long piece of hose here.

If you're using 1/4" braided PVC like me, the hose will probably fit well enough to make a seal, but not tightly, and it's a good idea to put a hose clamp around it. That will ensure that it doesn't lose its seal, and that it doesn't slip off. (Under vacuum, it probably won't lose its seal because vacuum will suck it inward onto the barb; if it slips off, though, you're hosed.)

Now attach the new check valve to the barb:

(1) Make sure the arrow on the check valve is pointing TOWARDS the pump, so that it will allow air flow INTO the pump, but not back out through the intake.

(2) Insert the appropriate end of the barb into the litttle piece of hose. It should be snug; work it in most of the way.

Once that's done, you can attach the long remainder of the hose to the other barb, in the same way; the other end is what you attach to whatever you're sucking from.

Now you have a vacuum pump. Try it out.