How to Replace a Septic Field

If there's damage to your septic system and you need to replace your septic's drain field, be prepared. You will need to either rent a back hoe or dish out some major cash. Septic system work is expensive no matter which way you look at it, but it must be done. Here are the basics of replacing a septic system drain field so you know what to expect.

Instructions

1. Determine your septic system's flow rate. Most likely the amount of outgoing water is going to be greater than what your tank and leach field were originally designed for. Make sure you consider all water using appliances into the calculation, as well as any future improvements, such as an added bathroom, that you may be planning.

2. Do a perc test. Perc is short for percolation. This test determines how fast the ground absorbs effluent. If your percolation rate is high, for instance 1 inch of percolation in 4 minutes, your leach field can be smaller, about 5,000 square feet depending on your flow rate. But if you have a percolation rate of 1 inch per hour, you'll need about twice that space, again depending on your flow rate.

3. Dig your field. Now that you've determined the septic system's flow rate, percolation and field size, dig trenches 18 to 30 inches deep and 8 to 12 inches wide depending on the design.

4. Add gravel into the trenches about half of the way up. A perforated pipe, connected from the main septic, will run along the center of the trenches.

5. Lay your perforated pipe. You have several pipes up to 150 feet long, laid in parallel lines across the field in your dug trenches. Lay these at a flat grade, or even a slight upgrade, to ensure effluent doesn't flow directly out of the end of the pipe. If this is not done right, all your work is lost and it will have to be dug again.

6. Backfill the septic system field. First cover the perforated pipe with stone, then cover that with filter fabric and backfill with topsoil.

Tips & Warnings

• Be sure to dig your trenches about 6 feet apart. If you ever have to do this again, you can put a new pipe in between the existing pipes in the field, and not have to dig the whole field again.

• This is only a general outline of what is involved in septic design and leach field construction. There are minimum distances you must be from the water table, other structures and between effluent pipe. Make sure you consult your local sewage enforcement office for your local building codes and requirements.