If the Quooker singletaps tap leaks, this can have 2 causes.
- Is it leaking at the spout? (where the water normally comes out)
Then you need new internal parts
Internal Parts Singletaps- Is the tap leaking under the handle?
(see image)

then the tap is defective, there will be a crack in the tap body.
This cannot be fixed, you will need a new Quooker system.
The Singletaps Quooker taps are no longer available and the new taps do not fit the old type reservoir.