Why does the grinder pump in an approx. 3'x3' tank stop working intermittently? It's worked and then stopped. When we open up the tank lid and touch the float, it activities the pump and the tank empties. We messed with the float a little, but not much. Could it be the float? Could the pump be going bad? We know it's older than 7 years, and it could be 2 or 3 times older than that. We've replaced the switch. The old switch seemed to work properly, i.e. making the clicking noises if you changed positions for the float arm. Is there a way to test the pump if it is going bad before we replace it? Any thoughts? Thanks.