I have a push button toilet, and the cistern has stopped filling. Water is entering the cistern, though slowly. I filled it with a bucket, and 5 minutes later it was empty, so I think it's not holding the water, it's trickling down into the toilet. Can anyone advise? Thanks!

The push button still operates a ballcock in the tank/cistern. You may have two problems so lets start with the flapper. Check it for irregularities and debris on both the black rubber flapper and the plastic rim it seats on. You aren't getting agood seal on the flapper but they are cheap and easy to replace. The slow fill is another story. Reach inside the tank and move the ballcock down, the fill should have some good pressure and noise. If not the ballcock valve and/or the angle stop cock coming out of the wall may have debris and must be opened and cleaned. If you want more details of this just ask otherwise I'll assume you've done stuff like this before.

Thanks for the fast reply. My cistern doesn't have a flapper, it has a blue plastic tube that looks like narrow plastic drain pipe that raises to flush when you push the button, then drops back in place.

Check the blue tube for any build up, debris or out of round shape. Also check the hole it drops into to make a seal.

Thanks so much for your help.