Constructing a septic system for an RV can be accomplished by building a scaled-down version of a full size system. A smaller septic system will work for an RV because usage is lighter than that of a septic system built for a house. You can build a simple yet effective system with products purchased from your local hardware store, plumbing supply and stone yard. Check with your local zoning office for required permits.
Locate the main sewer pipe coming from the RV.
Attach a 5- to 10-foot piece of PVC pipe to the main plumbing pipe coming out of the RV. This pipe extends horizontally and should be attached with a clamp which can be removed easily to travel with RV.
Measure the distance from the inlet hole to the bottom of the tank. This measurement needs to be the depth of the hole from the bottom of the pipe.
Dig a hole and set the tank in it according to your measurement.. This is the septic tank, which will separate the solid and liquid waste.
Fit the inlet from the RV drain into the tank until it is snug.
Level the tank and backfill the dirt around the tank.
Glue an elbow onto the end of the drainpipe facing down toward the bottom of the tank.
Dig a 10-foot ditch from the end of the tank at the outlet hole, pitching down 1/8 inch per foot.
Install PVC pipe from the outlet hole to the end of the trench.
Glue a PVC elbow on the outlet pipe in the tank facing down toward the bottom of the tank.
Dig a 10-foot-deep hole at the end of the trench.
Add stones to the hole. Fill the hole up to the bottom of the pipe.
Add a 2-foot length of 4-inch PVC perforated pipe to the end of the PVC solid pipe. The perforated pipe should end in the middle of the stone filled hole and slope down 1/8 inch per foot.
Cover the perforated pipe with stones. Stones should surround the pipe and be at least 4 inches above the pipe.
Apply rosin paper on the stones to separate the dirt and the stones. The rosin paper will eventually dissolve once the dirt is packed, and at that point the dirt will not mix with the stones.
Put the lid back on top of the tank.
Backfill the dirt into the trench and grade.