To me, a cesspool does not have a drainfield and allows sewage to “seep” into the soil. A septic tank does not have holes. Rather it holds sewage until the solids (toilet paper, etc.) settle to the bottom of the tank and only liquid flows out of the tank and into the drainfield.
Obviously, the drainfield system will last longer, because most of the solids remain in the bottom of the tank and will often decompose...then flow out into the drainfield.
The size of the drainfield depends on 1) type of soil, 2) slope of site, and 3) how often the wind blows., and 4) size of tank.
1) Granular soil is better than clay. They’ll do a percolation test on a sample of soil.
2) A sloping site could require a switch back layout, and solid pipe is used on the sloping portions and perforated pipe is laid flat. Yep, it’s laid flat because you want the liquid sewage to flow evenly to the entire system.
3) Little known fact: liquid in the pipe flows into the gravel (which is in the trench around the pipe) and the wind blowing across the site (and average outdoor temperature) will help the
moisture evaporate. The depth of the pipe and amount of gravel (1’ wide trench or 2’ wide trench) around the pipe is critical to the efficiency of the system.
4) Bigger tanks will allow the sewage to decompose longer before getting pushed out into the drainfield. A drainfield works on the principle of water flowing out of the tank every time you flush the toilet or take a shower and send more liquid into the tank. Having a bigger tank allows everything to decompose longer. Having a “healthy tank” like @Ed Beal says means allowing the microbes in the tank to eat the solids. Too much laundry detergent, kills the bugs. That’s bad for your system. (You can buy power to counteract detergent and flush it down the toilet each month. Then it stays health and you won’t need to pump the tank...ever.
Your local Environmental Protection Agency (EPA) or Department of Environmental Quality (DEQ) will determine the design and length of drainfield. (By the way, it can’t be too close to a property line or too close to a well.)
The size of the septic tank and length of drainfield will determine how many bedrooms you can have. (They don’t care about how many bathrooms, the number of occupants determines the impact on the system and that is determined by the number of bedrooms. So, if you have a 2 bedroom house and want a 3 bedroom, move a bed into that storage room, or basement area before they come out to your house. They can’t reduce the number of bedrooms, but they can prohibit adding bedrooms.