You have a low water pressure problem. Once you clean the baskets and filter you will need to check for plugged lines on your suction and for a clog in your impeller on your pump. If your pump basket is cracked the impeller is the place to start. Reach into the pump, with the basket out go through the hole in the back of the pump pot with some long nose pliers and feel for anything in there. If you can't pull it out with the pliers then break the pump down and see if you can clear it then and run a wire through the veins on the impeller. Then if it still has problems you may have to replace the pressure switch on the heater. This is seldom the problem, it is more of a warning to tell you of the other things that may be wrong.