Our house has one of those two-chambered standard (Philippines) open-bottom septic tanks. I think it's also called a cesspool.
I got into a discussion with someone on whether it can get full. Their argument is that, since it's open, the sewage can drain freely into the ground. My response is that the solid waste would build up over time.
I tried to research it online, but I can't find any information specific to open-bottomed septic tanks, other than pages and pages of "How to know when your septic tank is full" results.
Do they become full? If so, why and around how long?