Most septic tank systems work on gravity. Each component of the septic system must be slightly lower than the preceding component in order for the system to function properly. When the slope of the property or the distance from septic tank to the field line is too great, the system must be powered by other means.
When gravity cannot be used, a submersible pump is installed into the septic tank in order to transport the liquid from the septic tank to the distribution box of the field lines. Not only will this type of system require a pump, it will also require a different style of septic tank and a different size drain line.
Septic Tank Pumps
The pumps used in septic tanks must be fully submersible and must also be heavy duty. While the liquid being pumped out of the tank will have been processed, it may still contain small pieces of dirt or debris. Most pumps will also be single phase and work on standard 115 volt house current.
The outlet port on the pump is a standard two inches in order to accommodate the smaller drain line used in these types of septic systems. Normally, a four-inch PVC pipe would be used to carry the waste water from the septic tank to the field lines. With a pump unit, this drain line is normally reduced to a two-inch diameter pvc pipe.
While different size pumps can be used, a one-half horse power unit is fairly standard. Depending on the model and type of pump purchased, you should expect to pay in the neighborhood of $300 for the pump. If at all possible, this pump should be on an independent electrical circuit for added protection.
Septic Tank Styles for Pumping Units
With a normal gravity style septic system, the septic tank has only a single chamber. This style of tank will not work with a pump. The solid waste and sludge which is found in the standard septic tank would quickly clog the pump and cause a complete system failure.
When using a pump in a septic tank, the septic tank will need to have two chambers. The first chamber works in exactly the same manner as a single chamber tank. The waste product enters the first chamber and is broken down by bacteria, leaving only a liquid. This liquid slowly flows into the second chamber where the pump is located.
The pump in the second chamber of the septic tank is activated when the water level reaches a pre-determined depth. This is generally accomplished by using a flow switch. Once the pump is activated, it will pump until the water is removed, then shut off until it is once again activated by the float switch.
Cleaning a Pumping Septic System
It is critical to keep the solid waste and sludge contained within the first chamber of the septic tank. If the sludge levels are too great, some of the sludge will enter the second chamber, possibly causing damage to the pump.
On a normal septic system, the septic tank must have the residual sludge pumped/cleaned out approximately every three years. With a pumping unit, you will want to install an inspection port for the first chamber, which will allow you to monitor the sludge build-up and have the tank cleaned on a regular basis. This will prolong the life of the pump and the entire septic system.
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