Conventional vs aerobic vs mound septic cost comparison
Three common system types, three very different price tags. Enter your quote for each and the tool flags the lowest and the gap to it — but remember your soil may force the choice.
Calculator
On your figures the lowest option is Conventional at $8,000.00. Type choice is not just price — a mound or aerobic unit is often required by soil, water table or lot size, so confirm what your site allows with a designer and your local health department before you compare on cost.
Formula
A plain A-vs-B-vs-C normalizer on your figures:
lowest = min(conventional, aerobic, mound)delta(type) = cost(type) − lowest
The tool sorts the three costs you enter, names the cheapest, and shows how much more each of the others costs. It compares only price — it does not decide which type your site is allowed to use.
Worked example
Quotes of $8,000 conventional, $14,000 aerobic and $20,000 mound make conventional the lowest. Aerobic is +$6,000 and the mound is +$12,000 over it. If your soil rules out gravity, though, the real choice is between the aerobic unit and the mound.
Cost is not the whole choice
The three types suit different sites. A conventional gravity system is the simplest and usually cheapest, but it needs suitable soil and enough vertical separation to the water table. An aerobic treatment unit (ATU) injects air to treat effluent to a higher standard, allowing a smaller or shallower field where soil or space is tight — at the cost of a blower, more parts and ongoing maintenance. A mound (raised) system builds an engineered sand mound above poor or shallow soil or a high water table, and is typically the most expensive because of the fill, the pump and the extra construction.
Crucially, the choice is often not yours to make on price: a failed perc test, a high water table, shallow bedrock or a small lot can require an aerobic or mound system regardless of cost. Confirm what your site allows with a licensed septic designer and your local health department before you compare quotes. Use the informational type labels here (conventional, aerobic, mound) as a guide, and price the winner in detail with the new-system estimator.
Basis: a comparison of the three costs you enter — a planning estimate, not a bid or a design recommendation. Soil and site conditions, verified by a professional, govern which type is permitted.