Well, depends on what it's filling up with. If it's full of water then that's a good thing because any septic tank that is not full of water has a leak. As far as (sludge) goes then that is a different story. Products such as Rid-X and others work very well. They are a bacteria that "eat" up the solids in the tank. Believe it or not a properly working septic system should never need pumped out. So what are you pumping out? If it's mostly water then you are wasting your time and money.