If you find the levers on the two way brass tap adaptor are not shutting off the water, or seem stiff or hard to adjust, it may that the levers are a little tight and need loosening. This is only usually prevalent when using the product for the first time.
To resolve: Use pliers to twist the lever so that if fully shuts off the water for the first time. Then, if you twist the levers back and forth gently a few times with the pliers this should loosen it and shut off properly the next time.