So is it leaking from the hoses? I usually soak the ends of the pipes in boiling water for about 30secs before pushing them on to the valves, then i screw them down. It gives a better seal as the pipe is softer.
If its just leaking from the outflow pile znd not the actual filter head then its more likely the hose not on fully. Check for splits at the end of the hoses too. If you find one just cut the hose back an inch or so then reattach it.
They are good filters. Keep me posted