replacing the stab valve should resolve the problem.
But first make sure that the leak is not coming from the O ring seals at the water connections of the stab valve. If the stab valve has been disturbed it is easy to get a leak at the O rings. Going by the screws in the stab valve cover its likely to be a Triton manufactured product, sold by wickes/or other DIY store. For a replaceement stab valve contact Triton
garryk
February 2010