When you first start making soap at home, you may wonder why your soap recipe calls for distilled water and not tap water. As it turns out, not all water is created equal, especially when it comes to soap making.

It’s natural to want to save money when you first start making soap. It’s great to save money by using what you already have, but can you safely use tap water to make cold process soap?

Most of the time you can safely use tap water to make cold process soap. The key is understanding what type of tap water you have. Minerals, added chemicals and contaminants in some tap water can interact with the sodium hydroxide making your soap lower quality, but it will still be safe to use.

While your soap is safe to use when it’s made with tap water, there are some pretty significant reasons you might choose an alternative. What begins as a way to save time and money, might cost you much more in the end.

I’ll even let you in on one of my own personal soap making “oopsies.” It has to do with water, stinky feet and soap, but not in a good way – more on that later!

But first, let’s go over some of the things you’ll want to know, and some tips for choosing your water, so you can confidently start your next batch of soap.

Using Tap Water to Make Soap

Experienced soap makers know that every single ingredient plopped into your soap pot has the potential to interact with one or more other ingredients. That’s the fun “sciencey” part of the process! Because of that, it can also cause unwanted problems.

Most tap water is monitored for pathogens, so making soap using tap water is almost always safe to use for washing. However, there are many different qualities of tap water that can affect the outcome and quality of your soap.

Think of it like this. Everything in your tap water besides the H2O, can be imagined as an additional ingredient to your recipe! Let’s go over some of the things found in tap water and the possible effects it might have on your soap:

#1 Tap Water Minerals Can Cause DOS

The more minerals you have in your water, the harder it is. Soft water is devoid of most minerals. You know you’ve got soft water when you shower and the water makes it feel like you can never get the soap rinsed off all the way. Harder water usually tastes better thanks to the mineral content.

When making soap with hard water, the minerals can contribute to DOS or “dreaded orange spot” an ugly, but harmless, oxidation of some of the soft oils in your soap recipe. They can also inhibit lather.

Another problem that may be directly related to using tap water is the annoying white film that sometimes develops on top of your soap called “soda ash.” It’ harmless, but does a fine job of ruining your design. Learn more about preventing soda ash here.

#2 Chemicals in Tap Water End Up in Your Soap

There are many municipalities that add chlorine to their water supply to kill harmful pathogens, making the water safer for the public to drink. It can be added to water as a gas or in the form of hypochlorite either as liquid or solid.

Where I live, the type of chlorine used is supposed to evaporate off if the water sits for 30 minutes. It may not have much of an effect on soap making, but it’s a less natural approach.

Fluoride is another common additive. Some people prefer to eliminate this from their water completely and have even installed filtration systems that guarantee they won’t drinking it, or even showering with it.

While not intentionally added, sometimes trace amounts of pesticides and even prescription drugs can be present in the water.

Depending on the types and levels of these chemicals in your water, they may react with your other soap ingredients by changing the color, or contributing to rancidity.

More importantly, most people want to use homemade soap to avoid chemicals, not be exposed to more of them!

#3 Tap Water Can Cause Inconsistent Soap Making Results

The quality of your water can change over time, so what works today might not on your next batch of soap.

When making your own soap there are PLENTY of things that can go wrong! (Fragrances can accelerate, ash forms on your soaps for no apparent reason, etc.)

It’s hard enough troubleshooting things that go wrong with your soap without the added question: “Did my water cause the problem?”

When you make your soap with tap water, you might have a much harder time figuring out what happened with a less-than-stellar batch of soap!

To sum it up, the most important thing in determining whether or not to use tap water in your soap is knowing the quality of your water. If you have softer water with less chemicals, you are more likely to get away with using it for making soap. If you have a high end filtration system already installed at your tap, you have a greater chance of success.

The Real Cost of Using Tap Water to Make Soap

The biggest problem with using tap water when making soap is that it can ruin your batch of soap and that can be a lot of money wasted!

Some soap oils and additives, such as essential oils, can be expensive! You may not even realize it’s been ruined until your soap has fully cured 6-8 weeks later.

You might not find out it’s happening right away or even attribute it to the tap water until you have MULTIPLE BATCHES made! That can get expensive fast. Plus, think of all the wasted work time. Yikes!

When you use tap water to make soap, you risk losing expensive ingredients and lots of labor.

Alternatives to Tap Water for Soap Making

You may have decided that based on the quality of your tap water, it really isn’t something you want to risk. I know it’s tempting to use tap water, especially if you ran out of distilled water and don’t want an extra shopping trip for just one thing.

Here are some alternatives that might cross your mind, so let’s take a look at them:

Distilled Water – The purest and best type of water for soap making. It doesn’t have minerals or contaminants and is pretty inexpensive. It costs around $1 a gallon. It will give you the most consistent results.

Bottled Water – It can have some of the same issues as tap water. Plus, it’s something you are going to pay for. It’s almost always more expensive than distilled water, so I wouldn’t bother with regular bottled drinking water.

Filtered Water – A better option, but you are still buying filters.

Milk – Milks are a great alternative, especially goat milk. You won’t have the problems with contaminants, plus it adds some extra-luxurious properties to your soap. It’s more time consuming, since you will need to freeze it and slowly add the lye to keep the milk sugars from scorching.

Remember how I told you we were going to talk about stinky feet? Well, I had this really ultra-brilliant idea one spring afternoon. Hearing the thunder roll in, I grabbed a few stainless steel pots from the kitchen during a big rain storm.

Carefully, I lined them up out in the open on our large backyard deck and waited for the magic to happen. After a few hours, I had enough rain water to filter through a clean shirt. I was so excited to make rainwater soap!

Everything went perfectly, or so I had thought. Several months after cure, instead of smelling like “clean cotton” fragrance, my soap morphed into a “sweaty gym sock” fragrance. It was the only batch of soap I ever used rainwater with and the only batch that ever turned out like that.

Lesson learned. Rainwater has pollutants and contaminants, too. And that’s what it did to my soap. Rainwater isn’t a good option, unfortunately.

Some Final Tips

If you want to save a little on water cost, you can do a water discount. Basically, that means using a little less water than the recipe calls for.

Just remember the less water you use, the faster your soap will reach trace. You also want to make sure you use at least as much water as you are using in lye, by weight.

There’s another added benefit to using less water – it helps cut down on soda ash. Find more useful tips and tricks for preventing soda ash here.


6 Comments on Making Soap with Tap Water: 3 Things You Must Know

  1. what about purified water or does that follow under the same category as filtered water? Great article btw.

    • Hi, Michelle! Yes, purified water is a type of filtered water. It’s definitely better than using tap water in soap making. Steam distilling the water does the best job at removing the most impurities and minerals, so it’s the best choice for making soap. By using the best water it reduces the chances of contamination that can eventually cause your soap to become rancid or go bad. That said, I have used tap water to make soap with no problems since I live in an area where we have pretty good water. If purified is all you have access to, chances are it will be fine.

    • Hi, DJ! Water from a water softener system would be better than plain tap water, especially if you can run it through a filter as well.

  2. My soap turned out weirdly fluffy or soft (maybe even crumbly???) this time. Just realized used tap water and maybe that why it failed. I tried googling what went wrong, but didn’t see anything addressing my situation. Could tap water do that?

    I don’t know if I should just wait till it’s had a chance to harden or try to rebatch it. What is your suggestion?

    • If it’s crumbly, it may be lye heavy. If it’s soft, the lye may be going bad and not be full strength which would cause more of the oil mix to remain unsaponified. (If the lye is bad, it has a grey-ish tinge to it and it won’t heat up as much when you mix it with your water.) The main thing you want to be careful of is if it’s lye heavy. It is possible that the tap water contributed to the issue, but if you normally have pretty good tap water I would say it’s something else. Also, some oils take an incredibly long time to harden or can make a soap soft or rubbery. A castille recipe (uses only olive oil) can be really soft at first and takes 6 months to cure, whereas, too much castor oil can be rubbery. BTW – my apologies for such a long wait for a response. I hope you found out more as it cured 🙂

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