A month or so ago I started to get a noise when flushing the downstairs loo. It=92s a loud-ish hum that starts when the cistern is about half empty and lasts for about 5 =96 10 seconds. The hum stops if I turn on the cold water tap on the sink. (I=92m pretty sure both are fed off the mains.) The pipe inlet to the cistern also vibrates slightly while the noise is happening. When the cistern=92s empty I can make the noise happen for a few secs by lowering the ball c*ck to about half way.
I=92ve taken the top off the cistern and can=92t see anything obviously wrong. The cistern is probably about 10 years old. Any ideas?
Michael