If you have a backup the first thing to do is lift the lid on your tank and check the water level. The water level in your tank should always be 6-8" from the top.
A common misconception is that when your level is that high, your tank is "full" and needs emptied - that is normal operating height and will always be at that level. If it appears to be at that level you likely have a plumbing issue inside the house.
A common place for it to get plugged is the inlet leading from the house into the tank. Sometimes you can get it unplugged yourself by checking that location.
If the liquid is right up to the lid/overflowing then you could have a tile bed problem. You will need the tank pumped. Your filter could also be plugged. Newer systems, with 2 chamber tanks, have filters that need cleaned annually.
