What are the different types of septic systems?

The five main types are: conventional gravity (most common, $3,000-$7,000), chamber system ($4,000-$8,000), aerobic treatment ($10,000-$20,000), mound system ($10,000-$20,000), and sand filter ($6,000-$18,000). Your soil type and local codes determine which you can use.

Which septic system is best?

Conventional gravity systems are best if your soil percolates well. If you have poor soil, high water table, or limited space, you may need an aerobic, mound, or chamber system. Your county health department will specify what is allowed.

Updated 24 March 2026

Septic System Types: Cost, Pros & Cons

Your soil type determines which system you can install. Here are the five main options ranked by cost.

System Type	Install Cost	Maintenance	Best For
Conventional gravity	$3,000-$7,000	Low	Good soil, adequate space
Chamber	$4,000-$8,000	Low	Areas with high water table
Sand filter	$6,000-$18,000	Medium	Poor soil, near water sources
Mound system	$10,000-$20,000	Medium	High water table, shallow bedrock
Aerobic treatment (ATU)	$10,000-$20,000	High	Small lots, poor soil, strict codes

1. Conventional Gravity System ($3,000-$7,000)

The most common and cheapest option. Wastewater flows by gravity from the tank to a drain field of perforated pipes buried in gravel trenches. Bacteria in the soil naturally treat the effluent.

Requires: Good soil percolation (perc test), adequate yard space (500-2,000 sq ft for drain field), and low water table (4+ feet below drain field).

Best choice if your soil qualifies. Simplest, cheapest, fewest moving parts.

2. Chamber System ($4,000-$8,000)

Uses plastic chambers instead of gravel trenches. The chambers create air space for effluent to contact soil. No gravel delivery needed, which reduces installation time.

Advantage: Works better in areas with high water tables and variable soil conditions. Easier to install in tight spaces.

3. Sand Filter System ($6,000-$18,000)

Effluent is pumped through a sand bed for additional treatment before reaching the drain field. Produces very clean effluent, suitable near sensitive water sources.

Requires: A pump (adds electricity cost of $50-$100/year) and periodic sand replacement.

4. Mound System ($10,000-$20,000)

An elevated sand mound is built above natural ground level. Effluent is pumped up to the mound where it filters through sand and soil. Used when the natural water table or bedrock is too close to the surface.

Downside: Expensive, visible mound in your yard (3-5 feet high), requires a pump, and needs periodic mound maintenance.

5. Aerobic Treatment Unit ($10,000-$20,000)

Essentially a mini wastewater treatment plant. Injects air into the tank to promote aerobic bacteria that treat waste more thoroughly than conventional anaerobic systems. Produces very clean effluent.

Downside: Highest maintenance. Needs electricity ($50-$100/year), annual professional inspection ($200-$500), and mechanical parts that fail. Not a "set and forget" system.

Required by some counties when conventional systems are not permitted. Often mandatory for small lots or sensitive environmental areas.

How Your Soil Determines Your System

Before installing any septic system, your county requires a percolation (perc) test ($200-$500). This measures how fast water drains through your soil:

Perc Rate	Soil Type	System Options
1-30 min/inch	Sandy/loamy (ideal)	Conventional, chamber
30-60 min/inch	Moderate clay	Chamber, sand filter
60+ min/inch	Heavy clay	Mound, aerobic, sand filter
Failed perc test	Rock/impermeable	Aerobic or mound only

The bottom line: You do not always get to choose your system type. Your soil and local codes decide. If conventional is allowed, take it. It is the cheapest, simplest, and most reliable option. If not, budget $10,000-$20,000 for an alternative system.

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