Indesit IWDE126 washer/dryer

[Philipio]

When drying, this machine's water inlet solenoid valve keeps opening briefly just for a split second, every 20 to 30 seconds. It is audible, especially if you pull the detergent drawer open. It causes a knocking noise in the airing cupboard which comes from the mains water inlet piping. Any ideas anyone? Is there a filter somewhere which might be blocked or something simple like that? Or something more serious?

Have you had it long? Is it still under warranty? By having a look online it would seem it's not that unusual in a variety of Indesit washer/dryer models - see the youtube link below. Is it properly balanced/level? If it isn't, that can cause all sorts of weird vibrations,sounds,etc.