Washing Cloth Diapers in Hard Water or Soft Water: What’s the Big Deal?

By April Duffy •  Updated: 05/18/24 •  8 min read

What is Hard Water

About 85 per cent of North America has hard water, which is water that has high levels of calcium and magnesium minerals. The more calcium and magnesium you have in your water, the harder your water is.

Of course, even if you geographically have hard water, you may have municipal water that has been treated to be soft, or a home water-softening unit.

What is Soft Water

As you might expect then, soft water is simply water that has low concentrations of calcium and magnesium particles.

But don’t be fooled, if you have soft water, you may actually have a tougher time with your laundry than those with hard water, so keep reading! 

How is Hard Water Measured?

Water hardness is most often measured in Parts Per Million (PPM). It can also be measured in Grains Per Gallon (GPG), which can then be converted into PPM if needed.

Why Does It Matter?

Water hardness is a sliding scale, and what you consider “hard” water or “soft” water usually depends on the business you’re in. If you’re in the pool business, you’re shooting for a calcium level of about 100-400 parts per million (PPM) to avoid wear and tear on your pool’s parts (Source).

If you’re trying to sell water softening systems on the other hand, anything at or over 180 PPM is probably horrible and needs a very reasonably priced water softening system immediately (Source).

For our purposes, hard and soft water have dramatic effects on how laundry detergent behaves. Hard or soft water can cause your detergent to either be powerless in very hard water, or so powerful it builds up and causes problems like smells and rashes in soft water.

Calcium and magnesium always affect detergent, but as always any problem with regular laundry is magnified when speaking about cloth diaper laundry. Regular laundry, things like sheets and t-shirts made from single-layer of fabric with maybe some surface dirty, are WAY more forgiving than diapers, which have many layers, some of which are water-resistant, tightly sewn together and soaked in human waste, often for days.

For cloth diaper laundry, here are the ranges that we’re concerned about: 

PPMRangeChanges to Laundry Care.
0-25 PPMExtremely SoftExtra rinsing and care will be needed on top of detergent reduction.
25-125 PPMSoftDetergent will need to be reduced and an extra rinse added.
125- 180 PPMModerateRecommended detergent amounts. Extra rinse if desired.
180-250 PPMVery HardDetergent will need to be increased. No additional rinsing after main wash.
250+ PPMExtremely HardWater softener (i.e. Borax, Calgon) will be needed to boost detergent. No additional rinsing after main wash.

As you can see from that chart, washing cloth diapers in very soft water, and washing them in very hard water are two completely different processes. The first, requires little detergent and lots of rinsing, the latter requires lots of detergent, possibly water softeners, and no additional rinsing.

In a nutshell: it’s a big deal.

How to Find Out if You Have Hard Water or Soft Water

Ok, so if water hardness is a big deal, how do you find out how hard your water is?

There are many ways, many of them free, and all of them cheap:

1) Ask Your City

If you’re on a municipal water supply, your city may have up-to-date information on the hardness/softness of your water, and just a simple phone call or email to their offices may be all you need to do.

2) Take A Sample To Your Local Pool/Spa Shop

If you are on well water, or if your city doesn’t have water hardness information to give you, the quickest and cheapest way to find out if you have hard water may be to take a water sample into a local pool or spa shop, which is often free.

Pool and hot tub owners have to monitor their water conditions constantly in order to use their pool or hot tub chemicals correctly. Many pool and spa stores will offer water testing for free or almost free to customers. Taking a water sample in and having it tested for hardness (and ph while you’re there) will only take a minute, so if there’s one close by, you can have a result in the time it takes you to get there.

Make sure to take your sample from the same pipes going to your washer; often that’s a wash basin next to the machine. This is because if you have a water-softening unit in your home, it may not run to your basement washing machine. The closer to the source, the better.

3) Ask Your Local Pet/Aquarium Shop

Just like pool owners, aquarium enthusiasts need to monitor their water too. You can have your water sample tested at one of these shops, often for free, as well.

Once again, make sure to gather your sample from the same pipes going to your washer; often that’s a wash basin next to the machine. This is because if you have a water-softening unit in your home, it may not run to your basement washing machine. The closer to the source, the better.

4) Test It at Home

If you can’t get out to a store, and you’re either not on city water, or your city doesn’t have a hardness reading for you, you can still test your water at home with simple test strips for very little cost.

Single Hard Water Test Strip

You can get simple, and easy to read strips like these on Amazon here or even Walmart here.

The Best Detergent for Cloth Diapers in Hard Water

Pretty regularly, the Cloth Diapers for Beginners community will have a member post to ask what detergent is best for hard water.

The answer is simple: none.

While many other cloth diaper communities like to make a big deal about this detergent being good for this water, and that detergent being hard to rinse out because it’s missing unicorn dust or whatever, it’s not a matter of what detergent you’re using, it’s about how much you’re using (and how many dirty diapers you’re washing too).

Aside from the basic rules of choosing a cloth diaper detergent, which you can read here, the important thing is amount you’re using; which will be affected by your water hardness.

I have a whole post to help you figure out exactly how much your detergent you need in your cloth diaper wash here. In it, you’ll find a link to a “detergent calculator sheet” I designed to help you along the way.

What About Hard Water Build-Up On Cloth Diapers?

Another concern that often comes up is that leaks are being caused by someone’s hard water.

If the amount of detergent being used is off, and the diapers are being washed in hard water, it is possible for hard water deposits (calcium and magnesium) to build up on cloth diapers and cause a problem.

But, and it’s a big but, it’s rare.

Why? Because those diapers are going to stink like crazy, and be dingy grey long before the buildup is so bad it causes repelling. A mom would have to have a nose of steel not to know something is up before long.

The Bigger Problem: Soft Water

A much bigger problem with cloth diaper washing is soft water. Modern washing machines have changed, drastically, in the past 30 years, but our habits around laundry haven’t yet.

It was true, a long time ago, that more soap could get laundry cleaner.

Not today.

Modern HE washing machines use very small amounts of water (it’s their selling point!) and so adding in a ton of detergent to your laundry, especially if your water is soft and that detergent doesn’t have heavy calcium and magnesium particles to attach to, can be a big problem.\

Detergent easily settles on fabrics and builds up quickly. It also doesn’t smell when fresh out of the dryer, after all, every top layer is clean detergent. But after awhile, inserts will smell like ammonia when wet, and before long they can even begin to repeal water, though rashes often occur first.

If you think you may have detergent build-up, you find out how to test for and remove it here.


When it comes to hard and soft water and cloth diaper care, the bottom line is that it matters, a lot.

Testing your water hardness will be one of the best things you can do to care for your cloth diapers.

Once you know your water hardness, you’ll be empowered to create an optimal wash routine that will not only keep your diapers clean, but keep mineral build-up and detergent build-up from happening.

More Help if You Need It

If you feel like you need more information about wash and care, and would benefit from some step-by-step guidance, I will recently launched a digital book called the Cloth Diaper Wash and Care Handbook.

The handbook is not only a guide to cloth diaper wash and care, but it’s also a simple workbook designed to help you effortlessly build the perfect wash routine for your unique water and lifestyle. 

It’s the guide that should have come with your cloth diapers.

Get the Wash & Care Handbook

April Duffy

April is the founder of Cloth Diapers for Beginners and author of The Cloth Diaper Wash & Care Handbook. Since 2015, April has helped well over 75,000 parents and caregivers cloth diaper their children through this website, her book, her YouTube Channel, and the Cloth Diapers for Beginners Facebook Group.