Foghorn sound - driving me nuts!! Help

Surrey, not toooo far away but just DIY.

 

Recently swapped the Part 2 valve and cleaned the ball for an elderly neighbour rather than replace the washer. Left the section that connects to the tank alone and just unscrewed the valve from inside the tank and replaced that section, with the water turned off it took 10 minutes max.

 

Psssst - it's an easy DIY fix

And you've done this already on your cistern

But, of course, if you are happier getting a plumber in, that's fine.

The 'thud' you mentioned when something stops filling is usually down to a certain type of filling valve, not the 'ballcock' type. The ballcock type tends to come to a slow stop as it fills, so no 'shock' when it finally shuts off. But there's another type of valve which looks very different and this fills at the same rate all the way up until it shuts off quickly. I think this type is more likely to cause the 'thud', although it shouldn't if everything is ok.

Mind you, the noisy valve might also be 'loose' inside so this causes the thud as it moves when full.

When the plumber replaces it, give it a test refill whilst he's there to see if that thud remains. If it does, he should be able to trace the cause quite easily, I'd have thought.

 

An old thread, but I've got the foghorn vibrations AFTER putting in a new float valve. The previous one was silent but worn and the overflow was dripping constantly. All the same symptoms - noise happens as the cold water tank on the loft fills, but is eased by lowering the mains pressure (by opening a cold tap). Reducing the pressure via the main stopcock lessens the noise a bit, but the pressure is already quite low. How can a new valve be faulty?