Keep at it and you should get 60%+ out of an air still usually 700ml from a 4 litre wash of 14%. The higher alcohol % you can get then the cleaner the spirit and a better taste or lack of it remembering of course that you will always be cutting to your prefered drinking strength. This principle is why you will hear on the forum of people cutting to 40% and then putting it back in for a second run the first run being the "Stripping Run". The best way to look at it is if it's 60% Alcohol then it's 40 of other stuff so if you cut it back with water and do it again the 40% other stuff is mostly water. Hope that makes sense?
Opus 27