Septic Repair - System Replacement
Complete Septic System Replacement
This depends on whether or not there are trees that have to be removed to make room for the new drain field. It also depends on whether or not the water table is less than 3 feet from the surface. A high water table usually causes your replacement drain field to be elevated above the present grade of your lawn or yard. Here is a picture of a yard before drain field installation. When the job is finished, the lawn will be 2 feet higher than before.
Follow our photographs to see how the replacement septic system and drain field are installed. This is a front yard before construction. The lawn has already been disturbed by soil evaluation deep hole tests.
The septic construction company follows the design drawing of the replacement drain field. The drawing specifies that the top soil (Layer A) and subsoil (Layer B) must both be removed. The construction company knows that the drawing says remove 28" of soil. But what if the actual depth of the top soil and subsoil is different in one part of the drain field than in another part of the drain field ? Should they remove 28" no matter what ? The construction company can also refer to the descriptions of soil color and soil texture of these upper soil layers provided on the drawing to confirm that they have removed all of it. In this location, the top soil consists of soil, stones twigs and branches which were put there when the house was first built. Usually, these upper soil layers are much less compact than the original underlying soil. We do not want the replacement drain field to be built on top of these disturbed Layers A and B. The disturbed soil may not necessarily be consistent throughout, and as a result may distribute waste water unevenly. Note the distinct color differences between Layers A and B, and the color of the underlying Layer C.
Once the drain field area has been prepared, any soil that has to be brought in for the drain field, can be placed. In this case, a black plastic membrane will be used to add stability to the sides of the elevated drain field. Adding extra stability to the earthen side slopes is used because the drain field is not far from the house on one side and the public street on the other.
The black plastic membrane can be challenging to put and keep in place. This company used wood stakes to hold up the barrier, until they are done placing the sand up against it.
Build the Drain Field-Day 4: Haul in the coarse sand and disperse across the drain field. Generally, we do not want the heavy equipment on top of the drain field. But, in this case, there is no room in the yard and the excavator has to work from within the drain field area.
A closer view of the sand brought to the construction site.
Build the Drain field - Day 5: All of the sand has been brought to the property, and spread across the drain field. The plastic barrier was placed to reach above the sand, to the top of the plastic disposal chambers.
Build the Drain field - Day 5: Septic tank delivery and placement completed. The contractor will connect pipes to and from the septic tank after the drain field disposal chambers and distribution box are in place.
Build the Drain field - Day 6: The drain field plastic chambers are easily placed over the sand. In this drain field "bed," there is no separation between the rows of chambers.
Build the Drain field - Day 6: After the drain field chambers are set at the system designer's specified elevation, the distribution box is set on a bed of gravel and the 4" pipes are placed. The pipes are then connected to the D-box and to the septic tank. The contractor may wait till the drain field is ready to receive liquid effluent before they connect the septic tank to the house plumbing.
Note that the contractor manually compacted the soil around the pipe (see the footprints) before covering the pipe with soil. This helps the pipes remain in place while fill is deposited over them. Sometimes, these pipes vertically bend under the weight of the backfill. Vertical bends can create dips and valleys in the pipe. Waste water could collect in these pipe dips and cause problems during freezing temperatures. This contractor likes to use sturdy Schedule 40 PVC pipe to lessen the chances of this happening. The Schedule 40 pipe costs more, but is worth it, if it saves aggravation in the future. Digging up frozen pipes in the winter is not fun for a contractor, and is not cheap for whomever is paying the bill.
TIP for HOMEOWNERS: If any painting or drywall work is being done in the house, then it is most critical that the plumbing not be connected until the interior work is completed.
Build the Drain field - Day 7: Drain field has been covered with loam and topsoil. Low rock wall has been built to hold soil back from the driveway at the far end of the drain field.
Build the Drain field - Day 35 The yard has been seeded, grass is now established. The vent pipe has been painted dark green, making it less noticeable. Ornamental plantings have been added to de-emphasize the raised grade.