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

Step 5 Remove the check valve parts from the hose connection fitting

Now examine the hose fitting carefully. There's an oval cavity inside it, and a little metal ball that can move back and forth in that cavity. When it gets sucked toward the pump on the upstroke, it makes a seal, but when it gets blown toward the hose on the downstroke, it doesn't. This lets air out, but not in; it's what's called a "ball check valve," and it's built right into the hose barb fitting.

(You probably can see the ball, just barely, when you tip the hose barb down... it rolls almost to the end of the hose barb, and stops short when it hits a couple of extra bits of metal, which partly block the end of the hole.)

To get the ball out, you need to make the hole as big as the ball all the way to the end of the barb.

The straightforward way to do that is just to drill it with a 1/8" drill bit; just drill down into the hole to take away any extra bits of metal that retain the ball, and you can roll the ball right out.

For my Slime 2060-A, it was easier than that. I noticed that there were a couple of slivers of metal on opposite sides of the end of the hose barb, which had just been bent inward to make the retaining parts. All I had to do was bend them outward again.

I did that by inserting a screw into the end of the barb, and turning it with a screwdriver while holding the fitting with a wrench. The threads of the screw gripped the two bent-in pieces of metal and pulled them outward enough to make room for the ball to come out. (For other pumps of a generally similar old-school design, you may have to drill the hose barb to make the hole big enough to release the ball.)

Once you have the ball out, check to see if you have a hole clear through the fitting. There may also be a piece of rubber in there that needs to be removed. In my case, I tapped the fitting on the table a few times, and a little piece of rubber just fell out.

If you have a different brand of pump, you may need to drill yours to tear up the rubber, and blow the bits out. Drilling straight through fitting is not difficult, and may be a good idea anyway, if you want to go to the trouble. (See the next step.) Whatever kind of check valve is in there, drilling right through it is bound to help remove it.