Why does the pop-up on my sink's drain keep popping up?

Question

After 3 years of good service, the plug in the pop-up waste in a bathroom basin won't stay down/closed for more than 30 seconds. It takes me 2 minutes to shave, and in that time the plug pops up 4 or 5 times.

While it is closed the basin is water-tight and when it pops it drains at about the right speed, so I don't think it is the height of the adjuster under the plug at fault. It seems as though the weight on of the ball on the end of the control is pushing it down, but until 2 weeks ago this didn't happen.

What should I try adjusting to make it work properly again?

Answer 1

If you look under your sink, where the rod from the plunger enters the sink's drain, you'll see that it passes through a screw-on cap. Tighten that cap a little (not too much!) because it has come slightly loose. The cap holds a ball that the rod pivots around, so by tightening it you'll make the entire plunger assembly harder to move. Play with it a little until you get it how you like it.