Water Hardness: If you have hard water (water with high mineral content), you may need a little more detergent for it to effectively clean your clothes. In contrast, soft water allows detergents to work more efficiently, so less is needed.

Stains and Soil Level: If you’re washing heavily soiled laundry, a tablespoon might not be sufficient. For typical loads of laundry with light to moderate soil, though, it can be enough.

To get white and spotless laundry, you may also want to incorporate other laundry practices