> For the complete documentation index, see [llms.txt](https://swatplus.gitbook.io/io-docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://swatplus.gitbook.io/io-docs/introduction-1/structural-practices/septic.str/t_fail.md).

# t\_fail

An active system becomes failing as the biozone gets clogged and hydraulic failure occurs. A failing system automatically turns active during the simulation and septic parameters are re-initialized to default values after the specified number of days for rehabilitation. For testing long term failure, *t\_fail* can be increased as per the failing duration. The parameter [operation](/io-docs/introduction-1/structural-practices/septic.str/operation.md) should be set to 2 for simulating failing conditions.