Drainfield replacement in Missouri

The drainfield is where the treatment actually happens, and Missouri statute calls its components lateral lines. It is also the expensive half of the system and the half that fails quietly: solids carried out of a tank with failed baffles, years of hydraulic overloading, or a field that was undersized for the soil it sits in. Replacing it is a new build in miniature, which means it goes back through soil evaluation, design and permit rather than straight to a machine.

Where does the permit come into drainfield replacement?

A new absorption field is major work, so it is permitted and it starts with the soil rather than the excavator. The state standard sets the specifications for construction and the length of lateral lines.

Source: Section 701.025(6), Revised Statutes of Missouri, read 2026-08-26.

When do you need this?

Effluent surfacing over the field, which is the clearest sign it is done.
Backups that return within days of every pump-out.
A field that has been driven on or built over.
A tank replacement where the field turns out to be the real fault.

What drives the price?

The soil profile, which sets how much field the ground needs and whether a conventional field is possible at all.
Percolation rate, since the state standard requires an engineered design past sixty minutes per inch.
Depth to bedrock, which across the Ozarks is the constraint that most often pushes a design to a mound or a drip field.
Whether a replacement area exists on the lot, or the new field has to go somewhere awkward.
Restoration afterwards, since a field replacement rearranges a yard.

We do not print a price here. Septic work is quoted from a site visit and a soil report, and a number on a web page is a guess dressed as a fact.

What should you ask the contractor?

Has a soil evaluation been done for the new field location, and by whom.
Does the lot have room for a full replacement field, or does this design need a variance.
Is an engineered design required by the percolation rate here.
What is being done about the tank and the baffles, so the new field is not fed the same solids.

Get a free quote for drainfield replacement

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