System Type
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The System Type page is where you define the core configuration of your septic system. You work your way through choosing the fundamental building blocks of a septic system in a cascading fashion. You choose four components — discharge method, secondary treatment, primary treatment, and disinfection — and the wizard validates that the combination is allowed under the applicable design guidance. You’ll see a summary on the right as you proceed.
How the Selections Work
The four component groups are arranged in a cascading sequence:
- Discharge Method — choose first
- Secondary Treatment — options filter based on your discharge choice
- Primary Treatment — options filter based on discharge + secondary
- Disinfection Method — options filter based on all three above
When you make a selection in any group, the downstream groups automatically update. Options that are not compatible with the site data and your upstream choices are disabled (grayed out). If your current selection in a downstream group becomes invalid, the wizard automatically selects the first available option (if there is one!).
Discharge Method
The discharge method determines how treated effluent reaches the soil or receiving water.
| Option | Description |
|---|---|
| Elevated Sand Mound (ESM) | A raised sand/aggregate bed built above natural grade. Used when the soil depth to limiting zone is insufficient for an in-ground system. The most common mound system in Pennsylvania. |
| At-grade — sloped top | An at-grade system where the top of the absorption area follows the natural ground slope. |
| At-grade — level top | An at-grade system where the top of the absorption area is leveled regardless of natural slope. |
| Eljen GSF Mound | A modular geotextile sand filter (GSF) system manufactured by Eljen Corporation. Uses engineered modules instead of loose aggregate. |
| Stream Discharge | Direct discharge of treated effluent to a surface waterway. Available only for designs that include secondary treatment and disinfection, and requires Professional Engineer signoff. |
The available discharge methods depend on your site data entered on the Site Investigation page.
Secondary Treatment
Secondary treatment provides additional effluent processing between the primary treatment and discharge. Not all systems require explicit secondary treatment.
| Option | Description |
|---|---|
| none | No secondary treatment. Effluent flows directly from the primary tank to the dosing tank and then to the discharge area. |
| Ecoflo Fiber Filter | A coconut-husk biofilter manufactured by Premier Tech. Provides advanced treatment that may allow reduced absorption area. |
| Puraflo Fiber Filter | A peat-based biofilter. Requires a dedicated dosing pump to deliver effluent to the filter modules. |
| Norweco HKBFR Bio-Film Reactor | An advanced aerobic bio-film treatment unit manufactured by Norweco. Used with Singulair 360 primary treatment. |
| Free Access Sand Filter (FASF) | A buried sand filter with removable covers for maintenance access. Requires a separate tank for the filter media. |
| RFS-III Sand Filter | A recirculating fine sand filter (RFS-III model). |
| Recirculating Sand Filter | A recirculating sand filter that passes effluent through sand media multiple times. Note: construction specs and drawings for recirculating sand filters are not included in the design output; a confirmation dialog will appear if you select this option. |
Primary Treatment
Primary treatment is the first treatment stage — typically a septic tank or aerobic unit.
| Option | Description |
|---|---|
| Septic | A standard septic tank. The most common primary treatment for residential systems. |
| Aerobic | An aerobic treatment unit that introduces air to accelerate biological decomposition. Aerobic primary treatment may qualify for an absorption area reduction. |
| Singulair 360 | A Norweco Singulair 360 advanced aerobic treatment unit. Typically paired with the HKBFR secondary treatment. |
Disinfection Method
Disinfection kills pathogens in the treated effluent before discharge. Most systems do not require disinfection.
| Option | Description |
|---|---|
| none | No disinfection. Appropriate for most soil-based discharge systems. |
| Ultraviolet Light (UV) | A UV disinfection unit that treats effluent with ultraviolet light. Required for stream discharge and some advanced systems. |
| Chlorination (CL) | Chemical disinfection using chlorine. An alternative to UV for stream discharge systems but generally also requires de-chlorination before discharge. |
Design Guidance
After selecting all four components, the wizard determines which design guidance category applies to your system:
| Guidance | Meaning |
|---|---|
| Standard | The system meets standard design criteria. No special justification is required. |
| Alternate | The system uses an approved alternate technology. A non-economic justification is required explaining why this approach is appropriate for the site. |
| Best Technical Guidance (BTG) | The system is designed under BTG provisions, typically for repair of an existing failing system. A justification is required. This is available when you checked the BTG box on the Site Investigation page. |
| Experimental | The system uses an experimental technology. A justification is required. |
| Professional Engineer (PE) | The system requires signoff by a registered Professional Engineer. A confirmation dialog will appear when you click Next. |
If the guidance type is Alternate, BTG, or Experimental, a justification text area appears at the bottom of the page. You must provide a written justification explaining why this system type is appropriate for the site. The justification must be non-economic — cost savings alone is not an acceptable reason.
Absorption Area Reduction
Some system configurations qualify for a reduction in the required absorption area. This reduction is NOT applied automatically. The area reduction can be elected on the Absorption Area Adjustments page.
Tips
- The summary area on the right side of the page shows the current system configuration and guidance type.
- If you receive a “Not a valid configuration” error, it means no design guidance covers the selected combination and data.