In certain situations two homes will be located in close proximity to one another, but the terrain will not be suitable to allow for two sets of septic field lines. While this is a significant problem, if both homeowners are willing to share a septic system, the problem can be handled fairly easily.

Sizing the Septic Tank

Septic tank size is determined by the number of bedrooms in the home. In the event two homes will be using the same septic system, the number of bedrooms in each home will be combined. In many areas the minimum residential tank size is 1,000 gallons. A tank with more capacity will be needed to service two residences. Likewise, the amount of field line required will need to be increased based on the perc test and the size of the septic tank. All of these measures will increase the cost, but not as much as paying for two separate systems.

Installing the System

Install the septic system in the normal manner. The tank--normally located approximately 10 feet from the foundation of the home--needs to be centrally located to prevent the need of excessive piping from one house. A simple Y joint should be installed prior to the pipes entering the septic tank so only a single pipe enters the septic tank. The remainder of the septic system should be the same as any other.

Maintaining the System

Homeowners will need to monitor the septic system closely for the first few years. An inspection should be completed after two to three years of service to determine how much solid waste has accumulated in the septic tank. This will help the homeowners estimate when the tank will need to be pumped out to prevent clogs, backwash and other serious problems. Pump out the tank when the reservoir is 35 percent filled with solid waste. On average this needs to be done every three to five years.

Source:

Homeowner's Guide to Septic Systems