The local septic tank cleaning company had a special, cleaning & inspection. It's the same company that put in our septic system. We've been having trouble, so Dh decided to give them a call. We found out what the problem is.
There is a filter, between the septic tank, and drain field, to protect & extend the life of the drain field. The filter has to be cleaned every 6 months to a year, depending on the situation.
We had NO idea there was a filter, or that it had to be cleaned (rinsed with a hose) periodically. It's not mentioned in any of the papers/booklets/owner's manuals/user manuals/ and brochures the owner gave us when we bought this home. Apparently the former owner was not aware of it either, because nothing has been done to the septic system since they installed it years ago, let alone cleaning the filter.
Once they cleaned the filter, they finished draining the tank. There was some sludge, but it wasn't as bad as I thought it would be, considering the previous owner did nothing to it. They put in a cleaner, that will remove all the sludge build up.
We're so glad he decided to call them.