Hardly any water has been coming out from my water filter system. I just replaced all three cartridges after there was not much water coming out. I have also emptied the tank and add air pressure to 40. Hardly any water comes out, only drips. My model doesn't have the flow restrictor tube that should be inserted and take out for every time you change the cartridges. What else can I do? I spent a lot on the cartridges ! Please help.