This problem is driving me nuts! The top tank for the hot water overflows at night time but is OK during the day. My conclusion is that there is a very slow leak when it should have shut off. I have bought 3 new valves. Took the first one back as defective, next one has same problem. Bought from another source - same problem. Our water pressure is very high . Could that be it? Any ideas? Would be most grateful. Fed up with wasting water and the drip drip drip from the overflow - torture! Thanks
The high water pressure could very well be causing the slow leak. Float valves rely on the pressure of the float to close a small valve in the stem. High pressure could allow for a little water to work its way through. A quality fill valve should be able to handle it. The fluidmaster 400 ARHR is a great low cost fill valve. You could also try a commercial fill valve. They are built to higher standards.