Hi,

For shampoos and soaps, most any will be fine. The main ingredients to avoid are lots of salts (that come in powdered detergents or cleaners) and boron/borax, also found in some cleaners or laundry detergents. Other than that, it’s more about your preference. I like to check products in the SkinDeep database, which shares toxicity info for human health. This is not relevant to reusing water for plants, but it’s something to think.

Happy grey-watering!