septic field chambers

Hey all,

I noticed on a septic map of my backyard that the county had on file there is a drawing...the field snakes off in the backyard, and there are what appear to be sections. There is a line from the tank to the first field section - it shows 4' to the first section, then that section is marked with a 5. Then there is 16' to a second section, and that is marked with a 17. Then the line makes a U-turn into a third section marked with an 8.

This is a photocopy, but it looks like there are segments within each section. Are those some sort of chambers or something? 5, 17, and 8 chambered sections?

Next - we have an issue that seems to happen just once or twice a year - during both heavy rain and heavy water use, the basement toilet won't flush. We wait a few hours and everything works fine for the rest of the year. If we added another one of these sections to the end of this drain field - could we pick up 25%+ imrpovement in the ability for the field to purge liquids?

I ask because we have 3 really young kids now and their water use is light. But when they get bigger/older - our water use will go up quite a bit I suspect.