Can You Reuse Bathwater in Japan? Why I Stopped Using Mine for Laundry

Yes, leftover bathwater can be reused for some laundry in Japan, but it depends on your washing machine, detergent, and whether you used bath additives. It should not simply replace clean water for every part of the wash.

When I first started living in Japan, reusing bathwater for laundry was one of those small household habits that surprised me.

Illustration of leftover bathwater being reused for laundry in a Japanese home

Some Japanese washing machines have a bathwater function, often labeled 「風呂水」, that uses a pump and hose to draw water directly from the bathtub. Seeing a whole tub of water after a bath, I could understand why people would want to use it again.

I tried it myself for a while.

But eventually I stopped. The method wasn't difficult; it just didn't fit the way I wanted to do laundry. These days, I no longer feel the need to reuse every tub of bathwater. If the bathroom needs a good clean, however, I sometimes use the leftover water there instead.

Can Leftover Bathwater Really Be Used for Laundry?

Using leftover bathwater for laundry is possible in Japan, but there are a few things to check first.

Kao, a major Japanese household-products manufacturer, explains that leftover bathwater can be used for the wash cycle with some regular laundry detergents. If the bathwater is very dirty, however, cleaning performance may be affected. Clean tap water should also be used for rinsing.

Bath additives are another consideration. If you used bath salts or another product in the tub, you need to check the instructions for both the bath product and your laundry products rather than assuming the water can be reused.

The washing machine matters too. If yours has a 「風呂水」 function, check its manual for the correct way to use the pump and hose.

So reusing bathwater isn't something I would describe as either good or bad. It is simply one household option, and it needs to match the products and appliances you actually use.

Why I Stopped Reusing Bathwater for Laundry

My reason for stopping was much less technical.

At first, I liked the idea of not wasting a bathtub full of water. But every time I did laundry, I had to take out the hose, place it in the tub, use it, and then put everything away again.

I didn't want to leave the hose wet, either, so drying and storing it became another small task.

After doing this several times, I realized that I had added an extra step to my laundry routine simply because draining the bathtub felt wasteful.

I also became less comfortable using water we had already bathed in to wash clothes. That was a personal preference, not a claim that properly reused bathwater is unsafe.

Eventually, I stopped doing it.

Living in Japan has taught me that I don't have to adopt every household habit just because it seems economical. Sometimes you try something and discover that it doesn't suit your home.

Two ways of reusing leftover bathwater in Japan for laundry and bathroom cleaning

How I Use Leftover Bathwater for Bathroom Cleaning

Eventually, I found a much simpler use for leftover bathwater: cleaning the bathroom itself.

If I know I want to clean several bathroom items the next day, I don't use bath salts or other bath additives that night.

After bathing, I sometimes use the remaining water to soak the bath stool, bathtub cover, bathroom cleaning tools, and the plastic slatted mat, or sunoko, that we use on the bathroom floor.

I also move the shampoo and body-wash bottles. When bottles sit in the same place for a long time, grime can build up around the bottoms and underneath them, so a bigger cleaning day is a good opportunity to clear the area.

For soaking, I sometimes use an oxygen-based cleaner containing sodium percarbonate, following the directions on the package.

I don't give a fixed amount or soaking time here because those instructions can vary depending on the product and the material being cleaned.

And soaking is not the end of the job.

Afterward, I take everything out one by one and scrub away any remaining grime with a sponge or bathroom brush. I sometimes use a little dish soap at this stage, rather than adding different cleaners to the bathwater together.

I even save an old kitchen sponge that is ready to be thrown away and give it one final job in the bathroom.

Everything gets a thorough rinse with clean water afterward.

Once the bath stool, bathtub cover, sunoko, bottles, and cleaning tools are out of the way, I wash the bathtub itself. By the time I'm finished, most of the bathroom has been cleaned in one go.

What to Check Before Soaking Bathroom Items

This is the part where I wouldn't copy another person's routine exactly.

An oxygen-based cleaner containing sodium percarbonate may be useful for soaking, but the directions and materials it can be used on depend on the specific product.

Some products sold in Japan list materials such as aluminum among the items that should not be treated with them. Bathroom products can also contain different combinations of plastic, rubber, or metal parts.

That is why I check the cleaner label and the item itself before putting something unfamiliar into the tub.

I also avoid treating several household cleaners as if they are automatically meant to be mixed together. If I use dish soap for the final wash, I use it separately after the soaking step.

The same caution applies to bath additives. A product being safe to use in the bathtub doesn't automatically mean its leftover water should be combined with another cleaner.

For me, the easiest solution is simply to skip bath additives when I already know I want to reuse the water for cleaning.

And after soaking, I always use fresh, clean water for the final rinse.

Reusing Bathwater Is Optional, Not Another Chore

I still drain the bathtub without reusing the water on plenty of days.

I no longer take out the laundry hose just because seeing all that water makes me feel that I should find another use for it.

But when the bath stool, bathtub cover, sunoko, and bottles are due for a clean anyway, I sometimes use the leftover bathwater before draining the tub.

I tried both ways after moving to Japan. Reusing bathwater for laundry didn't become part of my routine, but using it occasionally for a bigger bathroom clean did.

That is the version that has actually stayed in our home.

References 

  • Kao, “Can leftover bathwater be used for laundry?”
    Used to confirm guidance on using leftover bathwater for the wash cycle and clean water for rinsing.

  • Kao, guidance on using bathwater containing bath additives for laundry
    Used to confirm that product instructions should be checked when bath additives have been used.

  • Shabondama Soap, Oxygen Bleach
    Used to confirm product guidance for oxygen-based bleach containing sodium percarbonate and examples of materials that should not be used with the product.

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