DIY amateur here. The single handled plastic knob that controls the bathtub faucet recently fell off, along with a screw from its interior and a cap covering the screw. I wish I could post a picture, but the site isn't letting me upload them yet — even though I have plenty of reputation on the other stack exchange sites! (UPDATE: I now have the reputation to post pictures! See below).
A metal square receptacle remains in the center of the knob-less handle (I guess where a long screw affixed the knob), and the faucet itself still works fine; temporarily, I've put the old broken knob on the fixture and control the water flow. Of course, it keeps falling out.
I'd like to know if there's a simple fix I can do, or do I need to replace the entire fixture. If the latter, how difficult is this to do? I don't want to have to break tile, etc.
Best Answer
Depending on the manufacturer, the stem should be a free replacement. It's fairly trivial to replace.
If it's a common manufacturer, you should be able to exchange the stem at your local big box store or plumbing supplier.
Reinstalling is simply the reverse.
While picking up the stem, get an appropriate bolt to fit, and you're good to go.
Caveat: Figure out the manufacturer and call first.