How an employer will handle a negative/dilute result depends on the employer. Some employers will handle it as a hunky-dory if they like you well enough, while others will grant a retest, while still others will move on to the next applicant for hire.

FYI, niacin is an old myth. It does nothing to help pass a U/A. The same goes for AZO. Youve tested THC-negative because you have succeeded in reducing the concentration of THCA in your bladder by the water that youve consumed. The Niacin and the AZO had nothing to do with it.

Aspirin is old tech. Back in the day, it was used as an interferant for only one type of test: the first-generation EMIT screen. Since then, a second-gen EMIT was introduced to counter the interference issues caused by aspirin. As a result, the first-gen EMIT is seldom used by the labs anymore (if, at all). This is addressed in the Dilution "sticky" thread.