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Septic System Design

Septic systems require care in site selection, design and construction. Every individual conventional septic tank absorption field system must be designed and constructed according to State Board of Health regulation, 410 IAC 6-8, as explained in Residential Sewage Disposal Systems (available through your County Board of Health). A FACTS computer program is available at your local County Extension office that can make recommendations for several types of on-site septic systems for use with various site and soil conditions. If a conventional system is suitable for your situation, the program will provide the following design information: estimates of the septic gravel volume, total trench bottom area required, and depth to the trench bottom. It will also plot specific layouts of the septic field for various trench widths that will best fit the shape and size of the disposal area.


  • Identify soils to evaluate suitability for an on-site soil absorption field

  • Identify locations for the septic tank, feedline trench and centerline of all soil trenches

  • Determine spacing for trenches

  • Fence the total area required for the soil absorption field plus an additional distance of at least 50 feet downslope

  • Specify where a diversion ditch and/or subsurface curtain drain should be installed if the trenches are in the side or at the base of a slope and backfill with gravel



Paul Swoyer Septic's prepares and handles all paperwork needed to obtain the septic permit from the governing jurisdiction. We employ an engineer (P.E.) for all of your Residential and Commercial septic system design needs in central Texas. 

Medications taken by persons living in the home, bleaches, and non-eaten plastics and paper can also play havoc with the septic system.

Is there enough soil present in the drain field area? At least four feet of good soil (no rock or clay) is necessary.
Is there enough room for a drain field?
Is the ground level or is it sloped greater than 15%?
Is there sufficient drop from the house to the tank location and down to the drain field?

If a conventional septic system cannot be installed, then an aerobic septic system can be designed, which will not require test holes.


  • A plot plan or survey

  • Recorded warranty deed

  • Living Square Feet and number of bedrooms in the home/ Floor plan

  • 911 address (can be obtained from County Office)

  • For aerobic systems only, an affidavit to public form with signatures notarized and service agreement. Forms will be furnished by the installer.

Our engineer will need specific documents to design your septic system and to obtain permits from your county government.

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