Soap

Dear Home-Ec 101,
I was visiting my MIL recently and she told me that they have hard water, so she had to put a lot of extra soap in the washer because otherwise she didn’t get any bubbles and it wouldn’t clean the laundry. This confuses me because I always thought you weren’t supposed to have a lot of foam in the washer. I’ve read articles recently saying that most people use way too much laundry detergent. Also, the man who installed our new septic system told me that I should use liquid soaps because they didn’t foam and foam would not build up in the septic system (which is apparently a bad thing).

I suspect that my MIL simply doesn’t know what she’s talking about, but I would never say so to her. If I’m wrong, please correct me- or at least just clear this up so I can think about something else!
Signed,
Biting My Tongue

Heather says:

You are both partly right.

Laundry detergent isn’t just one thing, it is a blend of ingredients in either a solution or powdered form. Some of it is soap, some detergent, some surfactants, water conditioners, and then we get to the perfumes and dyes.

Hard water is water that has calcium and magnesium in solution and these dissolved minerals cause a lot of headaches in your laundry. If they are not suspended in water when the wash water or rinse water is drained, the magnesium and calcium can cling to clothing causing fabrics to feel stiff and dulling the color. Think of it a bit like looking through a slightly dirty window usually, you can’t focus on the dirt, but your view of the outside world isn’t as bright and clear due to the slight film obscuring the view.

It is often necessary to use more laundry detergent in hard water.

When laundry detergent is added to hard water, a number of the detergent molecules -which I’ve been describing ad nauseum of late- get used up binding the calcium and magnesium. This simply means that all conditions being equal, there will be fewer detergent molecules able to trap dirt in hard water than in soft water. Soap molecules that come in contact with minerals form our nemesis soap scum which is difficult to remove from wherever it decides to cling.

Please do not expect Home-Ec 101 to help you study for your physical chemistry final, I am only trying to get across basic concepts.

In chemistry, we often talk about something called the saturation point. When something is saturated, it can’t hold any more. In your laundry, this is the point at which no more detergent can be in the wash water. Whatever cannot be in the water falls out as precipitate. (Remember it like this, when it rains, it’s precipitating, the cloud cannot hold any more moisture so it falls out of the sky.)

Water can only hold so much soap, even if that detergent is busy holding minerals like calcium and magnesium in solution -the clusters of soap around oil or dirt are called micelles. So there is a point at which too much of anything is going to precipitate out of solution. Where that precipitate (dirt, oil, gunk micelles) goes depends on its density, it may sink or float on top of the water in a scummy layer.

As consumers, we tend to associate soap suds with laundry detergent doing its job.

Foaming and bubbles occur when air in your washer agitates, splashing the water around and trapping air. Bubbles and foam are actually two layers of soap sandwiching a tiny film of water. Air gets trapped in this film creating bubbles, as more air is introduced through splashing, you create the foam and suds we are all familiar with.

For the most part, suds aren’t coming in contact with the clothing and when the water drains, the suds leave a sticky film of soap behind. If there isn’t enough rinse water to bring everything into solution, those deposits will stay on the fabric which pretty much defeats the entire purpose of doing laundry.

People who live in areas with hard water do have a few tools at their disposal. 

Heat improves solubility.

Approximate Temperatures of Wash Water

Cold Water	Warm Water	Hot Water
65°F – 75°F	80°F – 105°F	120°F – 140°F
18°C – 24°C	27°C – 40°C	49°C – 60°C

In general, higher temperatures allow more soap or detergent to be in the water at a given time.

Additionally, please note that most laundry detergents aren’t going to be very effective at temperatures below 60°F or 16°C. If this is the only option, try dissolving powdered detergent in a small amount of hot water before adding it to the washing machine. This will help prevent those white powdery streaks caused by undissolved detergents.

Water conditioning

Those looking to improve the effectiveness of their laundry detergent in hard water can give conditioning their water a try. Water conditioning is the process of getting the calcium and magnesium out of the water where it won’t use up the detergent. This is typically done by exchanging the calcium and magnesium ions with those in salt (sodium and chloride).  Now keep in mind that some laundry detergents already contain ingredients, known as zeolites that condition the water.

Point of Use Water Conditioning

If you are looking to soften your hard water only in the clothes washer, be absolutely sure to purchase a non-precipitating water softener. Non-precipitating water softeners work best when added to the water before the detergent, this prevents the detergent from beating the water softener to those pesky ions. Yes, this means you will have to be more attentive to your washing machine when doing laundry.

Precipitating water softeners will cause the minerals to fall out of solution where they will likely cling to clothing and the inside of your washing machine, completely defeating the purpose.

Whole House Water Softening

Water softeners are a fairly common solution that also works by switching out the calcium and magnesium with the ions in salt by passing the water through a chamber of resin beads. These beads have to be recharged with salt on a regular basis. There are some environmental concerns with choosing to use a water softening unit and you should do your research thoroughly before making the investment.

Do not waste your time with a magnetic water softener.

You are not going to get the results you desire slapping a couple of magnets around a pipe. It’s a scam.

So for the TL/DR crowd to answer your initial questions:

1. Yes, you need more laundry detergent in places with hard water.
2. Soap suds are not an indication of how well laundry detergent is working and they can leave dirt behind.

Regarding Septic Systems:

Everything you allow to go down the drain affects the chemistry and bacterial balance of your septic system. Your septic system is designed to handle some variations, but if you go too far, you’ll upset the natural balance and end up with big problems.

Use the least amount of low foaming soap possible. The low foaming is critical for septic systems with an aeration chamber. As stated above, suds form when air is introduced to that soap film. Suds will leave behind soap and eventually clog the system.

And those of you who have septic tanks should remember that it is better to spread laundry out over the course of a week than overloading your system and upsetting the chemical / biological balance with a marathon laundry day. If you’re that far behind and the mountain of laundry is threatening to avalanche, consider saving yourself expensive septic repairs with the relatively cheaper laundromat option.

Send your questions to helpme@home-ec101.com

An image is linked with an affiliate code to Amazon.com. That image is used as an illustration of the system mentioned in the post, rather than a recommendation of a specific brand. . .