Rear Washer Squirts Once When Front Washers Used
 

This is for my son's 2010 Australian SP25 Manual.5 Door Hatch. Whenever the front washers are used a dribble of fluid is also initially squirted out of the rear washer jet. The combined pump near the right hand side (driver's side in Australia) has been replaced and that didn't fix it. Is this normal or is there a known fix? The resultant accumulation of washer fluid at the base of the rear windscreen is causing corrosion so we would like to solve it.