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How much does it cost to replace a drain field?

HomeAdvisor puts replacing a drain field (also called a leach field) at around $7,000, and installing one at $5,000 to $12,000 (HomeAdvisor, June 20, 2026). It's not a ceiling: HomeAdvisor's repair guide warns that a failed leach field can cost up to $20,000 to fix (HomeAdvisor, June 19, 2026). Repairing a cracked or broken lateral line is a smaller job: $1,500 to $5,000 (HomeAdvisor, June 19, 2026).

Estimate a complete mound system on poor soil →

What drives the price

• Soil and site. If the soil fails a perc test, HomeAdvisor says you can get a second opinion; if that also fails, the site has to be regraded or an alternative system installed (HomeAdvisor, June 19, 2026). EPA describes mound systems as an option for shallow soil, high groundwater or shallow bedrock (EPA, May 4, 2026). A complete mound system costs $10,000 to $20,000 to install (HomeAdvisor, June 20, 2026).
• System type. EPA notes that mound and sand-filter systems pump effluent from a pump chamber, and drip systems need a dose tank and electrical power (EPA, May 4, 2026), all of which add cost (see mound system cost).
• Testing and permits. HomeAdvisor says replacements need a professional assessment, and prices a perc test for a septic repair at $750 to $1,900 (HomeAdvisor, June 19, 2026). Whether you need one, and the permit, depends on your county (see permits by state).

Why drain fields fail

EPA explains that a natural layer of bacteria, the biomat, forms at the bottom of the trenches. In fields more than 25 to 30 years old it can thicken and reduce the field's ability to discharge water into the ground, which can cause ponding, surfacing sewage or backups (EPA, March 11, 2026). Other causes are solids escaping a tank that isn't pumped (EPA warns a clogged field may need replacing entirely (EPA, March 11, 2026)), too much water at once, and damage from vehicles or tree roots (EPA, August 17, 2026).

Signs the field may be the problem

• Standing water or soggy, spongy ground over the field, especially in dry weather (EPA, March 11, 2026).
• Bright green, spongy, lush grass over the field, even in dry weather (EPA, March 11, 2026).
• Sewage odors around the field (EPA, March 11, 2026). Slow drains and backups in the house are also on EPA's failing-system list (EPA, March 11, 2026), but they point to a problem somewhere in the system, not necessarily the field.

Some of the same signs can come from a tank that needs pumping, which typically costs $292 to $565 (HomeAdvisor, June 17, 2026). Have the tank checked too: see how to tell your tank needs pumping.

Repair before you replace

Not every soggy field is a dead field. A broken lateral line can be repaired ($1,500 to $5,000) (HomeAdvisor, June 19, 2026), and EPA's inspection checklist includes possibly using a camera to look at leach lines for blockages or collapsed piping (EPA, March 11, 2026) (see inspection cost). Get the diagnosis in writing and a second quote before agreeing to a full replacement.

Related questions

Sources

1. HomeAdvisor, Septic System Installation Cost, updated June 20, 2026.
2. HomeAdvisor, Septic Tank Repair Cost, updated June 19, 2026.
3. HomeAdvisor, Perc Test Cost, updated June 19, 2026.
4. U.S. EPA, Types of Septic Systems, last updated May 4, 2026.
5. U.S. EPA, Frequent Questions on Septic Systems, last updated March 11, 2026.
6. U.S. EPA, How to Care for Your Septic System, last updated August 17, 2026.
7. HomeAdvisor, Septic Tank Pumping Cost, updated June 17, 2026.