My Grohe toilet cistern doesn't shut off?

The water flows straight through my toilet cistern. My plumber has now replaced every part. Each time he replaced a part the cistern shut off when it was full but after a couple of days it stopped shutting off. He replaced a part recommended and sent by Grohe. It was fitted last Wednesday morning and worked perfectly until this morning and the water now flows straight through the cistern without filling up. I'm desperate!!
Joan, June 2016


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