My toilet is continuously filling but I can't find the float. There's the tube with the buttons, an overflow tube and a sealed grey box connected to a tube to the bottom of the cistern inside it. The grey box has CL and a line on it, so I presume it gets the level from there. But it doesn't unscrew or unclip easily so it's hard to tell. How can I adjust the fill level please?

is this it?

Unfortunately no. It's more like this:

But no hose.



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If it shut off at one time, but doesn't any longer, then adjusting the "float" will not work. But to adjust the level, you probably have to push the top unit down, twist the shaft, the push or pull the unit to the water level you want, then twist it back and pull up.

That type of ball cock is not approved in So Cal as it does not conform to ASSE 1002. So I would check to see if your building department allows such a device without an air gap to be installed in your toilet. The concern is backflow into your potable water system. Once the water is in your toilet tank it is contaminated and cannot be allowed to re-enter your system. A former neighbor now passed away, invented the first valve like that and it was turned down by those who approve such devices.



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The valve shown by the OP has a critical level marked on it and is adjustable to about the same heights as a Fluidmaster 400. It's not a drowned valve like Packy posted.