Here in Florida, a low pressure distribution system is required when the drainfield square-footage exceeds 1000 square feet. This system, like the conventional, consists of two components, the septic tank and the drainfield. The difference between the two is that this system has a distribution network setup inside the drainfield. It usually consists of 1 ¼” PVC pipe with specific sized holes spaced evenly the length of the drainfield. This type of system distributes a determined number of gallons of wastewater somewhat evenly throughout the drainfield. A pump is required in order to distribute the wastewater. This type of system can be installed in the traditional rock/pipe, chamber, or multi-pipe drainfield.
A low pressure system can be very expensive. This is due to the drainfield being very large. This system can be very labor intensive because the network of piping that is placed in the drainfield has to be put together, holes drilled and the pipe properly placed or hung in the drainfield product. In a mounded system the cost goes up due to the large amount of fill that has to be brought in to build the mound. The cost goes up even more when an excavation has to be performed beneath the drainfield. Excavations in mounded systems commonly exceed depths of 30 to 50 inches below the ground surface.
Aerobic treatment-drip irrigation systems are a more cost effective alternative as they occupy a much smaller foot print and are much easier and less time consuming to install. Mounds are dramatically reduced using this type of system. Excavations are significantly less and in most cases can be completely eliminated if an aerobic treatment-drip irrigation system is installed.