How are you determing when you need to dump?
Most tank level sensors work properly one time, The first time, after that stuff sticks to them and they give you a false sense of "Full" when in fact they may only have 10 or 15 gallons in them (Assuming a 40 gallon tank)
You may need nothing more than a good sensor cleaning. How to do it is fairly easy, and there is not much in the way of cost, however I'll leave the description of the process to the forum experts, in this, I'm not one