What does it cost to replace both a septic tank and drain field?
Last updated July 10, 2026
Short answer
Replacing a septic tank and drain field together in Windham County typically costs $10,000 to $20,000. Doing both at once is usually more cost-effective than replacing them separately, since site excavation and permitting overlap.
When a septic system fails, the tank and drain field often need attention around the same time, since they age together under normal use. Replacing both in a single project avoids paying for site excavation and permitting twice. Cost depends heavily on drain field size, which is set by the number of bedrooms in the home and the soil's absorption capacity, tested through a percolation test. A failing drain field on a difficult site, needing an engineered or alternative system, is the main driver that pushes a project toward the higher end of the range.