Building a new home with a septic system requires planning that starts at the lot evaluation stage — before construction begins.
Before purchasing a lot or beginning construction, commission a site evaluation. This includes soil testing, percolation testing, and water table assessment to determine what type of septic system your site can support — and whether it can support one at all. Some lots cannot legally have a septic system installed.
The septic system location must be established before the builder finalizes the site plan. The drain field and required setbacks affect where the house can be placed on the lot, where the driveway can go, and what landscaping is possible. Coordinate early to avoid costly changes.
Size the system for realistic future occupancy, not just current plans. Adding bedrooms later often requires a permit re-evaluation. If you plan to add a bedroom within 5–10 years, sizing the system now for that future capacity is much cheaper than retrofitting later.
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Use the Free Calculator →Before purchasing the lot, ideally. A site evaluation tells you whether the lot can support a septic system and what type. This fundamentally affects the value and buildability of the property.
From initial soil evaluation to permit approval typically takes 4–10 weeks. Complex sites requiring engineering review may take longer. Plan for this lead time in your construction schedule.
A licensed septic contractor, depending on your state's licensing requirements. The work must be inspected by the county health department before the system is covered and the home is occupied.
A failed perc test doesn't necessarily mean the lot is unbuildable — alternative systems (mound, ATU, drip) may be approved. A licensed engineer can determine whether any type of septic system can be designed for the site.