Blog    |    7 Steps to a New Plastic Septic System

7 Steps to New Plastic Septic System

Plastic septic tanks are just one significant piece of a wastewater management system in your home. It is essential to recognize and remember that when you are preparing for your plastic septic tank installation that there are several critical steps to take when installing a new septic system, and if you do not do each of them carefully, you may have some very expensive consequences to deal with later.

Step 1: Design Your System

The first step is to design your entire system carefully. There is some important information you will need to research and obtain for this. You will need a site survey to help you identify where the boundaries of your property are so that your septic system placement is in compliance with regulations about how close to your neighbor’s property the wastewater may flow underground.

The important pieces of information to look for in the site survey are:

  • the amount of space available
  • the topography of the land
  • the purpose and estimated use of water based on the size of your home, so you know how much water the septic system will have to process on a regular basis
  • the location of any wells on your property or neighboring properties

You will also need to do a percolation test on the soils in the area which your plastic septic tank installation will be located. This test is very important because it will determine whether the ground is suitable for a plastic tank and what type of structural precautions you will need to make to ensure that the plastic septic tank does not fracture or crack under the pressure of the ground around it.

The soil test will measure:

  • The type of soil and its contents (sand, clay, and rock)
  • Layering (where these soil types are within various depths)
  • How well the soil can drain and filter wastewater

Once you have these tests done, you will have the information you need to design an appropriate septic system for your home.

Step 2: Seek Permits

The second step for installation is to submit your designs and applications for the permits and approvals required by your local government. In order to receive approval of these plans, you need to comply with all the laws related to plumbing and building codes. Without these important approvals, you may be fined and forced to remove your system at great cost.

Step 3: Gather Equipment

Gather together the equipment required for you plastic septic tank installation.

Here is a list of the equipment and parts you will need:

  • Backhoe – this is by far the most efficient way to dig the holes you will need to lay your septic system in the ground.
  • Shovel – to help do some more precise digging in the holes you dig with your backhoe.
  • Laser transit – surveying tool to help ensure precise measurements for digging
  • Grade pole – surveying tool to measure accurate depth while digging.
  • (1) – 4″ Sch. 40 PVC pipe – input pipe from your home, which may require fittings as well.
  • (1) – 4″ ASTM D2729 perforated pipe – output pipe to disperse effluence into draining field.
  • (1) – 4″ASTM D3034 pipe with appropriate fittings
  • (1) – 4″ Sch. 40 vent caps and test caps – to disperse the buildup of gas from the decay of waste in the septic tank.
  • PVC primer and PVC glue – to seal and fasten PVC pipes together
  • Saw – a manual hand saw, or an electric hand saw to cut PVC pipe to necessary length.
  • Hammer drill with bits – this drill is needed if you have to drill through the wall of your house to install the septic system.
  • Hydraulic cement – this cement is used to seal between the PVC pipe and the wall of your house if you drill through it.
  • 1 ½ inch washed stone – to be placed below your septic system to ensure correct drainage.
  • Tape measures – you will need at least 100 feet of tape so it may be helpful to have a small and large tape measure on hand.
  • Septic fabric – You will need a roll cut about 3 feet long
  • Plastic Septic tank and risers – be sure that plastic septic tanks are allowed by your local regulations.
  • Silicone caulk – used to seal the risers
  • Septic filter – if it is required. See local plumbing regulations.
  • Plastic distribution box – used if you are operating a system with multiple laterals to the draining field.

Step 4: Install Intake Pipe

Locate the side of your home or building from which you want the septic tank to intake wastewater. At that place, you need to dig down at least 2 feet and either make a hole in the wall or dig deeper underneath the footing of the house or building. If you have a gravity fed system, plan the flow to go downhill since gravity fed systems do not use mechanical methods to move the waste from the tank to the drain field. It is important to realize the downhill slope needs to continue for a distance because the building or home plumbing can get the wastewater into the plastic septic tank, but it will not get it out of the tank and into the draining field.

Next, put the 4 inch Sch. 40 vent caps about a foot through the wall or under the footing and at least five feet outside the building or home, going toward the tank. It needs to be level at the wall and slope down about 1/8th inch per foot toward the plastic septic tank. You can take it all the way to into the tank if it is required, or you can then switch to 4-inch 3034. If you switch pipes, make sure you use the correct adapter as you attach it to the plastic septic tank.

Make sure you attach a test cap on the pipe end that comes out of the building. If you chose to drill through the wall, you need to seal around that hole with hydraulic cement, both on the inside of the building and the outside as well. It is important to keep the pitch of your input pipe right at a 1/8th inch per foot and no steeper and right around 5 feet out from the house. If the pitch is too steep, the wastewater will run too fast, and the solids will get stuck in the pipe. You may also have too little room left to sufficiently get the effluent into the draining field.

Step 5: Install Plastic Septic Tank

Dig a large hole that can fit your plastic septic tank below the ground. Use your laser transit to locate the top of the intake pipe and measure the distance from the top of the intake pipe to the bottom of the tank. Add that number plus 1 ½ inches to the measurement you got from your laser transit to your grade pole, and that should give you the depth that you need. Finish digging until you get to that depth.

Next, you need to dig out your draining field (or leach field) according to the specifications of your survey results and local regulations. Be sure that you keep enough slope to maintain an outward flow from your plastic septic tank installation to your draining field.

Step 6: Install Draining Field

Most places will require a 1 ½ inch layer of washed drain rock around the pipe to keep it steady while it moves substance. Your local health requirements will determine the size of gravel and the depth of this layer. When installing the perforated pipe in a gravity septic system drain field, remember that it has no slope on either end and is capped on its ends.

Step 7: Inspection and Filling In

Once you get the approval of your local health inspector, it is time to cover it all with soil. The drainage area will likely require a special fabric that acts as a filter, untreated building paper, or four inches of straw to cover your washed drain rock before you cover it over with soil.

Bonus for Pump Plastic Septic Tank Installations:

If you have a pumped plastic septic tank installation, there will only be a few differences in your process. Before you connect your plastic septic tank to your draining field, you will need to install a pump chamber. The pump chamber is set it up very similarly to the septic tank itself, but the electrical aspect of the pump will require a licensed electrician to make sure you are up to code for state regulations. Regions that have high groundwater may have an empty pump chamber most of the time, and some may require extra weight added to the floatation device that turns the pump on and off.

If you do the necessary research and tests on your property, submit your applications and designs for approval, and follow these steps, you should have no problem with your plastic septic tank installation. Do not start digging until you get your permits and ask for help from local septic experts at the first sign of trouble, not after you put everything together, fill it in, and find signs of leaking sewage when you first turn it on. If much of this tutorial sounded foreign to you, there’s no shame in asking for help! Reaching out to the experts early in the process will save you a lot of time, money, and the frustration of fixing an improperly installed septic system.

7 Steps to a new plastic septic tank system infographic

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