When we fulsh the toilet there is an awfullly loud squealing noise that carries , getting quieter until the cistern has filled. The noise stops if you turn on the sink tap while the cistern is filling but starts agaim if you turn the tap off - how can we cure this?

When we fulsh the toilet there is an awfullly loud squealing noise that carries , getting quieter until the cistern has filled. The noise stops if you turn on the sink tap while the cistern is filling but starts agaim if you turn the tap off - how can we cure this?

Which ballcock do you have? The one on the right or the one on the left? Let me know, Tom

Am not exactly sure as a new user if this is where I rely to Speedballs enquiry in response to my original question about my toilet squealing after we flush the cistern. I think we have a toilet with a similar cistern to the diagram you showed on the right with a floating ballcock. The squealing actually continues for about 30 seconds to 1 minute after the cistern has filled again.

Something's vibrating in your ball cock. Could be a small pebble or a piece of trash but whatever it is let's get it out of there.
Shut the water off under the cistern and unscrew the three screws on top of the ballcock. Pull the stem and float assembly up. Pry the washer out and seat it back firmly. Now place a pan over the ball cock and turn the water back on for a few seconds to flush out the supply. Reassemble, turn the water back on and give it a flush. Better now? Good luck, Tom

The ballcock is a solid polystyrene disc so there can't be anything in it. Any other ideas?

The ballcock is a solid polystyrene disc so there can't be anything in it. Any other ideas?
I've never seen a ballcock that couldn't be opened up and worked on. Could you post a picture of it? However, if it truly can't be opened up and worked on then replace it with one that can be worked on. Regards, tom