How to survive laundry with soft water

We recently wrote a post about hard water. This week’s post is for our friends with soft water.

In our detergent dosage calculator, we classify soft water as between 0-60ppm. This is a broad range that encompasses both very soft and moderately soft water. This post is for people with super soft water: 0-20ppm. Rainwater is this soft, and so is the mains water in some cities and towns.

In general, having soft water is a good thing. Your appliances and plumbing last longer without all the mineral buildup, your hair and skin are less dry, and cleaning is more efficient with less product used. However, when it comes to washing heavily soiled items such as cloth nappies, very soft water can make it difficult to balance using enough detergent and preventing whiteouts.

Matching detergent to soiling

The goal of any wash is simple: enough detergent to lift all the soiling and still have a little left over. That way, you know the wash has had enough cleaning power from start to finish.

A simple way to check if you’ve got the balance right is a suds check. Look at the front loader door around 30–45 minutes into the main wash. If you see:

• No suds = all the detergent has been used up, there was possibly not enough for the level of soiling (underdosed)
• Lots of suds = more detergent than the load needed this time. Reduce the dose slightly next time
• Some suds = the ideal balance. All the soil has been tackled by the detergent and there’s still some cleaning power leftover

If your machine goes into a suds lock, you can quell the excess foam by flushing some diluted fabric softener or hair conditioner down the detergent drawer. Suds will settle on their own eventually, but will take extra time or added rinses. 

The Goldilocks zone 👧🐻

The softer your water is, the smaller your ‘Goldilocks zone’. This is the happy medium between not enough detergent and too much.

You might find yourself second-guessing how much detergent to use. It can be a frustrating game of dodging whiteouts and battling stains that just don’t lift.

If you have constant whiteouts, our normal advice is to reduce the volume of detergent or laundry booster in future loads until you find the sweet spot to pass the suds check. But when you have very soft water, this can mean the detergent is reduced so much that there is not enough cleaning power to shift soiling.

Instead of tweaking the detergent dose, it might be better to switch the detergent type.

Why detergent choice matters

Powder detergents are made with a water softener base, most often sodium carbonate (aka washing soda). This means they bind to the minerals in the water, allowing your detergent’s active ingredients to work on the soiling on the laundry. It’s not uncommon for sodium carbonate to account for 30–50% of a powder detergent. 

Powdered laundry boosters include sodium carbonate too, as well as sodium percarbonate (oxygen bleach), which is the active ingredient that removes stains. When dissolved in water, sodium percarbonate breaks down into more sodium carbonate and hydrogen peroxide. You can see how this much water softening agents quickly become a problem for soft water households! 🫧

Unlike powders, liquid (and dilute-at-home) detergents don’t have a base of water softeners. This means they don’t result in premature sudsing, and allows a sufficient amount of detergent to be used to tackle stains and soiling. Whilst the lack of water softeners sucks for those who have harder water, if you have softer water, this is where liquid detergents shine.

Thus, if you’re battling suds in soft water, have stubborn stains that just won’t shift, and your laundry has that awful musty smell after a few hours, it’s probably time to try a liquid detergent and stop raging against the machine.

Tips for washing nappies in soft water

In summary, here are a few solutions you can try if you’re struggling with excess suds in soft water.

• Use a liquid detergent.
• Switch to chlorine bleach or liquid laundry boosters for added stain removal instead of powdered laundry boosters.
• Reduce the detergent in your nappy first wash first, before reducing it in your main wash.

With the right balance, you’ll get consistently clean clothes and cloth nappies, and a wash routine you can trust.