The amount of drainfield is different at each home. The bedrooms are the factor to determining the size of tank and amount of drainfield lines necessary. The local environmental health office will decide the size and location of the system prior to installation, which will be noted on the installers permit.
Septic systems installed after 1999-2000 were required by the state to have an outlet filter. The purpose of this filter is to retain all solids and particles in the tank. It does require periodic cleaning. This process keeps sludge from entering the drainfield lines. Once sludge enters the lines, it disrupts the percolation of the soil, which could lead to failure.