I am having this problem currently and would appreciate suggestions.

My toilet uses the Sheath Ballcock 1B1-X valve, similar to this:
http://www.homefixitparts.com/plumbing/P2-04-099B.php?part=P2-04-099B&dept=Plumbing

I replaced the valve recently, as it has needed it for a long time. After the replacement, I noticed that the toilet would be running after I got out of the shower. By the time I could look in the tank, it would shut off. Since then I have noticed it running at other times when other water is in use elsewhere in the house, such as the kitchen sink. It doesn't do it every time, just enough to keep me wondering.

Sometimes it runs long enough for me to get a look in the tank but I don't really see anything unusual going on in there. The water is down about 3/8" or so from the top of the overflow tube. It doesn't seem like water has drained out of the tank causing the float ball to go down and turn on the valve. It doesn't seem like it is trying to overfill either. I don't know what else to look for.

FYI, along with replacing the 1B1-X assembly I also had to replace the incoming water supply line. Everything else seems good, as far as flushing OK, no leaks, etc. Just this one issue is outstanding.

I am not even a novice plumber so please do not hesitate to suggest anything, no matter how basic.

THANKS,
-Marty
. Sorry, I forgot to post that I tried to do the test requested by speedball1. With the lid off the toilet tank, I turned on the shower and the bathroom sink and let them run for a couple minutes. I observed no change inside the toilet tank. However, when I turned them off, the float ball immediately jumped down a bit and turned on the toilet valve for about 15 seconds. So whatever it is, it seems to be happening when the water pressure to the toilet presumably increases due to the other draws on the water supply going away. Thanks in advance.

Hello MartinMarty, you have attached your question to other poster's thread. I moved it to give you your own thread.

Regarding your problem: First check pressure in your house. It should be around 50 psi.

Back to you. Milo

, I turned on the shower and the bathroom sink and let them run for a couple minutes. I observed no change inside the toilet tank. However, when I turned them off, the float ball immediately jumped down a bit and turned on the toilet valve for about 15 seconds.
BINGO!! Your air chambers. Shock absorbers ) are loaded up with water and must be re charged with air.

: The first thing I would do is to recharge the air chambers. We install air chambers on all lavatorys and the kitchen sink to reduce shock, vibration and noise. It could also be that a chunk of solder came loose and got caught in the bend of a 90 degree elbo and every time water rushes past the fitting it disturbs the flow. But I would try recharging first. Has this always been a problem or did it just start? Let me give you instructions on how to recharge your air chambers. Back in the 60's we were required to to put shock absorbers,(air chambers) on all bath lavatorys and kitchen sinks. Over time water and condensate built up in them and they must be recharged. First turn off the house at the main house shut off valve. Then open hot and cold faucets at the farthest bathroom to prevent air lock.(This is important.) You will find under each fixture little brass or chrome valves. These are called angle stops. With a small pail held under the angle stop to catch the run off look under the handle of the stop and you will see a nut with the stem running through it. This is called the bonnet packing nut. Put your wrench on it and back it off counterclockwise. Now open the stop and remove the stem and washer assembly, The stop will begain to drain. When it has quit draining reassemble the stop and move on to the next one. Do this on each one of your angle stops. There will be six of them. When you are done, close off the faucets you have opened, turn on the water to the house, and give yourself a pat on the back. You have just recharged your air chambers. If that don't get it click on back and we will go to step#2. Good luck and thank you for rating my reply. TOM