Water runs intermittently when toilet has sat idle

http://www.youtube.com/watch?v=ey3KBJKsGXI could be washer shown in youtube video is worn.
http://www.youtube.com/watch?v=jfp1zuLuIAg

had a toilet with this problem !

Check the fill valve. it may have a bad seal inside or some trash in the water supply (iron or calcium deposits) may have clogged it. Do you hear water running when it's not flushing?

If any toilet runs (continues to fill) when it is not being used, there are basically 3 reasons. the most obvious is that water is leaking out all over the floor so the fill valve thinks the tank has not reached its volume of water. Next, the rubber device that keeps the water in the tank when not being used (most commonly called a flapper) has warped from time or chemicals in the water (NOTE:chlorine eats rubber for breakfast daily), and and allows water to seep past it, which lowers the water level and triggers the fill valve to come back on to top things off.
The third reason is because there is particulat in the fill valve or mineral buildup and internally it doesnt always properly seal so it can run intermittently or all the time.
All the parts on the TOTO ultramax are warranteed for 5 years so keep that in mind if it applies.
Remove the tank lid when you hear the fill vave working and look at the water level. If the water level is below the top of the white plastic tube that the flapper is connected to (often called the overflow tube), then you have a bad flapper. If the water level is going over the top of the tube then you have a defective fill valve.
Out of warranty fill valves can easily be replaced with a Lavelle "Quiet fill" available at most hardware or plumbing stores or online.
This valve is what Toto uses in most of their toilets and it is only the removeable cap that is different (subliminal advertising maybe)

Place a few drops of food coloring in the tank of the toilet, if it is leaking you will see the color seep into the toilet bowl within a short period of time. If you see the food color in the toilet bowl you will need to replace the flapper.

There are usually generic parts available that will fit most toilets. If you can't find individual parts that will work with the assembly in the tank, replace the entire assembly.

The diaphram has a little metal by-pass or air-flow hole thats probally stopped up or the vacumn breaker is bad.

American Standard 2474016.222 also had the same problem mine had two discs apparently on efrom factory perhaps and one from the floating disc that must have fallen off I used a screw to get them out adn drained as much water as possible then went back and forth adding water a little at a time and then using a tolwel to sponge the water out (no shop vac around) After findign one I then found the other. This post saved me sooo much money adn I have dealt with the intermittant problem for years in this spare bathroom THANK YOU SO MUCH

You need to either bend the arm that connects tot he float down (if it is the type with the ball float) or adjust the height of the fill valve assembly. THis accomplished by slightly twisting the valve assembly carefully and sliding down a half of an inch or so and then twisting back to lock it in place.

This should fix you up right.

I suggest that you replace the cap with the new seal, it sounds as tho the valve is not shutting off and the bowl fill tube continues to run. Have you adjusted the water level to 3/4 of an inch below the overflow tube. If not, try that.

Did you replace the flapper with a genuine Toto replacement flapper? If you didn't, they are slightly different. Toto toilets are fantastic but you do need to use OEM parts for repair.