| Company | Location | Certifications | License # |
|---|---|---|---|
| B&B Riley Septic | West Plains, MO | Installer (Level Advanced) | 36994 |
| Brown'S Septic Llc | Mountain Grove, MO | Installer (Level Basic) | 33654 |
| Dc Plumbing Llc | Willow Springs, MO | Installer (Level Advanced) | 39447 |
| Dirtworx Land Management | West Plains, MO | Installer (Level Advanced) | 37355 |
| Drew Ince | Hartville, MO | Installer (Level Advanced) | 38551 |
| G7 Hauling & Excavation | Thornfield, MO | Installer (Level Basic) | 39133 |
| Harker'S Plumbing | Mtn. Grove, MO | Installer (Level Advanced) | 36144 |
| Harris Backhoe | Mansfield, MO | Installer (Level Advanced) | 34664 |
| Hogan Farms | Thornfield, MO | Installer (Level Advanced) | 33046 |
| Johnson Construction | Grainesville, MO | Installer (Level Basic) | 38934 |
| Mahurin Dozing | Mountain Grove, MO | Installer (Level Basic) | 38360 |
| Michael Spicer | Vanzant, MO | Installer (Level Basic) | 38516 |
| Mike Schumann Dba | Isabella, MO | Installer (Level Basic) | 38679 |
| Nicholas Schuette | Vanzant, MO | Installer (Level Basic) | 39509 |
| Owenby'S Backhoe And Septic | West Plains, MO | Installer (Level Basic) | 37336 |
| Sds Excavation | Isabella, MO | Installer (Level Basic) | 38953 |
| Simpson Excavating | West Plains, MO | Installer (Level Basic) | 38864 |
| Smith Excavation Llc | Gainesville, MO | Installer (Level Basic) | 35400 |
| Total Home Analysis | Springfield, MO | Installer (Level Basic) | 38501 |
| Triple B Farms Llc | West Plains, MO | Installer (Level Advanced) | 38451 |
20 companies in the Missouri DHSS registered OWTS installer list are based in Douglas County as of 2026-07-23. Companies based elsewhere in Missouri also commonly serve the county.
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