Can I use the Pure-Castile Soap with hard water?Updated 10 months ago

While you can use hard water to dilute our Pure-Castile Liquid Soap, it may cause your dilution to turn murky or opaque and you might experience some separation. However, this does not impact the efficacy of your soap.

The interaction of hard water, and even soft water, with any true soap (not synthetic detergent-based soaps), can also leave behind a thin film of minerals, also known as “soap scum.”

Hard water contains dissolved minerals in the form of calcium and magnesium. All true soaps, such as our Pure-Castile Soap, will react with these minerals to form insoluble stearates, which are visible as a whitish precipitate. This can slightly interfere with foaming capabilities and may leave soap scum on surfaces.

The whitish precipitate may build up primarily on surfaces where water is left to dry, such as sinks and showers. However, it is typically not an issue on floors, counters, or other hard surfaces where the castile soap is diluted for cleaning and standing water is mopped or wiped up.

Although you can dilute our Pure-Castile Liquid soap, it's not necessary for all uses and mostly comes down to preference. You may prefer just pouring a few drops into your hands for handwashing, and others may prefer to dilute our soap at a 1:3 ratio in a foaming pump. It's up to you!

If you would like to dilute our soap, we encourage you to only dilute a portion that will be used up within 2 weeks to a month, since we do not add any harsh preservatives in our products that will allow them to last longer than 1 month after being diluted. We also do not recommend using our soap in traditional pump dispensers as they tend to clog. Instead, try out a foaming pump.

For more information on using our soaps in hard water, we encourage you to check out Lisa Bronner's blog, Going Green with Lisa Bronner. Most notably her post The Chemistry of Water and Using Soap to Test for Hard Water.