Leaking toilet shut-off valve

At 2 am last night my toilet started to run. I was going to reverse the seal in the fill valve of my Kohler K-3434 to try to stop it, but when I turned off the water the shut off valve started to leak. I quickly turned it back on, and it stopped, and amazingly the toilet stopped running as well. When I get off work today I want to do a definative fix, if I can. What is most likely causing the shut off valve to leak when turned off, and what do I do to fix it?

It’s probably the valve-packing nut that requires tightening. Look for a nut at the base of the stem that connects the handle to the valve body. Tighten the nut SLIGHTLY, probably no more than 1/8th of a turn. This should solve the problem but keep an eye on the valve for the next hour or so to insure that the leak doesn’t reappear. Sometimes tightening the nut won’t help, as the packing material has been compressed to it’s maximum, or there is something else wrong with the valve. If that’s the case, it’s time to put a new valve on the supply line.

If and When you have to replace the toilet supply valve try to get a 1/4 turn ball valve. Full on or full off, and no packing worries. They come with lever handle or with two nubs to turn ball.

As a plumber, I agree about going with a 1/4-turn valve. Also, just wanted to mention that I’ve seen lots of brand new angle-stop valves leak water at the packing nut when you “wiggle” the handle a little. I routinely tighten them as part of the installation process.

If it’s just that the packing has been compressed to the point that it’s not doing its job, you can also try just putting some more packing in there. Cheap, easy, and sometimes effective.