Whether you connect to a public sewer line or a private septic system, your septic drainage system is an important element to your home value and to comfortable living. It is the guts and intestines of your home. With the added challenge of digging a 10 foot deep trench with a digger, laying sewer pipe is a difficult job for the amateur plumber, but it is an achievable challenge. Expert services should be sought, a septic design plan laid out, pipe material and tools selected, and the appropriate building permits and soil tests in hand. Know your local codes and regulations.
Design your septic plan (aka, drain waste and vent system, or DMV) so that the pitch of the sewer pipe you plan to lay will allow for proper drainage via gravity. Consider the soil type in which you will lay the sewer pipe; i.e., sandy, overly wet, clay. Pitch and soil type are factors in how you will trench.
Select pipe material: plastic (PVC often preferred over ABS), cast iron, clay or cement. You can also use a combination of materials in your sewer design. Judgement in the selection of materials will ensure an efficient lined sewer.
Hire a qualified technician to dig your trench (if you do not plan to do this yourself); generally the trench will reach a depth of 10 feet. Make sure your gradient drop does not exceed one-quarter inch per foot, or gravity will cause water to flow faster through your DMV than the solids travel, thus potential for plugged sewer lines. Again, local regulations will dictate requirements.
Remove loose soil before laying pipe so that pipe will not sag when you backfill the trench. Consider adding compacted sand or gravel bedding before laying pipes; this will offer pipes additional support from sagging.
Lower pipe carefully into the trench end-to-end; avoid getting soil inside the open ends. "Start at the low end of the run and work your way up to the connecting point," says contract plumber Nick Bougalis. Avoid going over a 45-degree bend in your pipe. "The overall efficiency of a drainage system depends on the last link, the run of pipe which ends the house system and connects with the main sewer or septic tank," Bougalis said.
Affix pipe ends with appropriate couplings and adhesive, applying steady pressure to fasten pipes straight. When using plastic pipe, sandpaper one end for stronger adhesion: use primer first then use PVC cement glue. If you are laying cast iron or concrete pipes then use rubber gaskets to seal coupling joints.
Arrange for your municipal inspector to come to approve the work before you close your trench.
Make sure bonding surfaces are free of debris. Do not forget to lay at least two septic clean outs.
Take great precaution when entering an open trench. This article is not intended to assume the authority of a trained plumber nor design engineer. Expert advice should be sought.