Suddenly the cistern is only filling after a delay from 2 to 10 seconds whereas it was immediate some days ago. I didn't touch anything and I'm sure noone entered my flat.

Not sure if it is a problem though as there isn't any leaking.

I don't know if it is linked but it seems this


doesn't serve any purpose since the cistern is filling whatever if it is open or closed.

Here is the best picture I could take:


  • Hello, and welcome to Home Improvement. We'll need more info before we can help you (e.g. is this a toilet? If so, what's the "faucet"? Pictures would help). And, you should probably take our tour so you'll know how best to participate here. – Daniel Griscom Jul 3 '19 at 11:37
  • Hi yes this is a toilet I thought the tag would suffice. Adding it to the title and a picture. Sorry I'm not an english native speaker so this lexical field is new to me! – MatTheCat Jul 3 '19 at 13:03
  • Thanks for your picture, and your English is certainly far better than my German/Spanish/Italian/Serbo-Croatian/Linear B. Would you mind adding a picture of the inside of the cistern? It might help understand just what that valve is. – Daniel Griscom Jul 3 '19 at 13:27
  • Just added a picture. – MatTheCat Jul 4 '19 at 7:35
  • ... are you sure the water is running through the valve? Might there be another supply line? Alternately, perhaps the valve is failing, and no matter what the position it's (somewhat) obstructing the flow. – Daniel Griscom Jul 4 '19 at 10:48

That valve is necessary for whenever you need to service the plumbing inside of the toilet, it turns the water supply off. In the cistern on the other end of that pipe coming from the valve, there is a "fill valve" mechanism of some sort, tied to a float. When the water drops down into the bowl to flush, the float drops and enables the fill valve to refill the cistern, until the level raises again and it shuts off.

Most likely your fill valve is getting old and is sticking when the level drops, so it shows up as a delay in that the float is not falling when it should. This would be an indicator that it is close to failing completely and needs to be fixed / replaced.

  • Thanks for the explanation. It seems the valve is useless because the cistern can be filled whatever its position. I'll try to look into the float. – MatTheCat Jul 4 '19 at 7:37
  • With the 2nd photo, I can see that the float and valve are essentially one unit, so you would replace them with an entirely new unit like it. – JRaef Jul 9 '19 at 0:20

I post my answer here because it would be too long of a comment but I'll accept J. Raefield's because he made me understand how it works.

For starters, call me dumb but I was convinced the valve closed by turning counter-clockwise. As I couldn't turn more I assumed it was closed which really was the opposite. So there is nothing wrong with the valve.

Now the float was in a mechanism where it slides into a plastic piece:

toilet valve

I guess some scale built up between the two and prevented the float to follow the water emptying. After I poured some white vinegar the problem went away 🎉

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