I just did a quick home repair and thought I would put it on the blockchain forever in case anyone has a similar problem. Our issue was that the tub drain would not stay open. When taking a shower, the lever would flip and your feet would be submerged. Googling around seemed to indicate that I should buy a new drain lever and faceplate, but when I took it apart a quick, simple, and cheap fix became apparent.
I started by taking the faceplate off with a flat head screwdriver.
The faceplate is actually attached to a long apparatus that is fished down the drain tube. Here's what it looks like when it's pulled out.
It's hard to see you because it's so corroded, but on the backside of the faceplate there are washers and a spring that use the tension from the spring to hold the lever in place. There are also cotter pins to keep everything secure.
I could tell that the spring wasn't providing enough tension, which is why the lever was just flipping back up whenever it was pressed down. I briefly thought about getting a new spring, but decided it would be easier to just increase the tension on the spring by adding an additional washer to compress the spring.
I pulled the cotter pins out, and luckily they didn't break when I was bending them. I was worried about that because they're so grungy. I was able to thread a new washer on and compress the spring while I replaced the cotter pin.
I put the counterweight back down into the drain tube and replaced the faceplate, and now the drain works. It's not a perfect or permament fix, but it should buy us a few years, and when the spring stops providing tension I'll just add another washer.
It ended up being a pretty simple job, and it saved me a trip to the hardware store, saved me 5 bucks for a new faceplate and lever, and I got the satisfaction of doing the job myself.