[Phil P]

Hi

It is possible for the tem change to cause enough expansion over time to push water by the toilet valve; some valves will leak under low pressures when they work under higher pressures.

I see the pressure buildup when the water heater is turned on to heat a tank of cold water and then the first time you open a hot water faucet the water is under more pressure than the rest of the system. The excessive pressure in only momentary but if there were a little air trapped some were in the system your 30 degree flux may be enough to cause this.

Phil P