Above Ground Septic Tanks
Above ground septic tanks are simply holding tanks
Above ground septic tanks, not to be confused with mound systems, or above ground septic systems, are not above ground septic systems at all, but simply holding tanks. Some decomposition will take place in above ground septic tanks, so tank must be vented to allow for expansion as well as displacement of air as additional waste is introduced.
As the name implies, above ground septic tanks, or septic holding tanks are designed to hold waste until a licensed sewage pumper can remove the contents, leaving them clean for future use. Since the average person generates approximately 70 gallons of waste water per day, above ground septic tanks must be sized accordingly. Another consideration would be to the color of above ground septic tanks in order to help it blend with it's surroundings, and possibly privacy fencing or lattice work to hide it. However, keep in mind that a tank which is difficult to access may require the septic pumping contractor to charge more. Time is money, so keep it simple for him/her to get in and out quickly.
See Plastic vs. Concrete Septic Tank for reasons why plastic is better for above ground septic tanks.
Above ground septic tanks can be gravity drain, or pump assisted.
The preferred placement of above ground septic tanks would obviously be lower than the drain lines leaving the home, allowing gravity to make the arrangement passive. If this is not an option, a pump tank will have to be employed which will be buried in the ground, or placed in a pit with manhole access. The pump starts and stops on level, and pumps sewage into the holding tank. Of course, this tank will have to be vented as well, and pump will have to be maintained, and an electrical connection provided.
Consider capacity and frequency of pumping when choosing above ground septic tanks
The septic pumper truck will be at least 1200 gallons capacity, which is not a super large truck, but it's regular access to your tank must be considered. A good question for the contractor might be how far will the truck hose reach, and is his pump sized to develop enough head to pull from the given distance. Placement of above ground septic tanks should be discrete, but accessible.