It does sound like it could be a pressure problem. Most fill valves should be used with 80 or less PSI. Evenings, when the water towers are filling, is a time of higher pressure. Terry

: We have a fairly new toilet, Cadet low-flush by American Standard, that has a strange problem. It runs on after flushing at night, but usually not during the day. Even stranger, running the cold-water tap in the sink (or even the kitchen sink) will stop the running on. I have adjusted the little screw, which got rid of the problem during the day, but it still runs on at night!! Is this a water pressure problem? What do I do?