Toilet cistern doesn't stop filling

[Deobrah]

The toilet doesn't stop filling up even if the water tank is full and keeps on overflowing the overflow pipe.

We've opened the toilet and the cistern looks like this. It's different from the ones I've seen on Youtube.

We've tried to adjust the height of the floating part by turning the screw clockwise and anti-clockwise. However, this did not help.
We've also tried to manually push the floating part up and down and this doesn't seem to block the water flow either.

Does anybody know how to fix this or what to test out next?

Thanks!

 

[CBW]

If the flush valve is t passing then it’s likely the diaphragm washer or part of the float valve that’s failed.

 

[Deobrah]

If the flush valve is t passing then it’s likely the diaphragm washer or part of the float valve that’s failed.

Thanks for the quick reply. Any recommendations on how to test this?

Do you by any chance know how this type of cistern is called? That might make it easier to find videos online.

 

[Wayners]

Take rubber out the filling inlet. Clean and put back taking note of how it comes apart. Good idea to get someone to film it or take loads of pictures.
Clean and put back together.

If that don't work replace inlet with known brand with brass thread.

You can buy just the rubber but not always easy to match up

 

[CBW]

Thanks for the quick reply. Any recommendations on how to test this?

Do you by any chance know how this type of cistern is called? That might make it easier to find videos online.

Cistern is concealed and the float valve looks like a Siamp. Easy way to test is to isolate the cistern, wait for the water to clear, place some dry toilet paper on the back of the pan and turn the water back on for the cistern if water gets onto the paper within a few seconds then it’s the flush valve, if it’s only when it starts to overflow then it’s the float valve. My money is on the latter.