What the Water Is, You Find Out on Arrival: Inside the 250 Stays With an Onsen

You stay somewhere with an onsen. You put your bags down and get in.

And you probably go home without ever knowing what the water was.

Two in ten say what the water is

Of the 654 listings, 250 have an onsen: 103 villas and 147 glamping sites.

We counted what those 250 say about the water itself.

	Listings mentioning it
Natural hot spring	85 (34%)
Spring type	48 (19%)
Free-flowing	34 (14%)
Diluted, heated or recirculated	3 (1%)
Stated benefits	3 (1%)
Water temperature	2 (1%)
Name of the source	0

That there is an onsen, you can tell. What the water is, mostly you cannot. One in five gives the spring type and one in seven mentions free-flowing water, of which 26 (10%) use the full term genzen-kakenagashi and the rest just say kakenagashi. The name of the source appears nowhere across all 250.

For the avoidance of doubt, this does not mean the other 216 are recirculated. It means the published information cannot tell you.

It is missing because it is posted on the wall

Under Japan’s Hot Spring Act, a property using onsen water posts the composition and the bathing notes inside the building. Whether the water is diluted, heated or passed through a recirculation filter belongs to that posting too.

Which means you can always read it once you arrive. It is usually by the entrance to the bath or on the changing room wall.

Its absence from the descriptions looks less like concealment than like the information having somewhere else to live. What does not need explaining on a website is posted on site as a requirement.

Put the other way: if you want to know at the booking stage, you have to ask. And asking works, because it is information they already display.

The three that do write it, write it plainly

Read the three that mention dilution, heating or recirculation and they split neatly.

Genzen Kakenagashi Onsen Glamping Akazawa Onsen in Tochigi puts it like this:

Free-flowing water from the source, undiluted and unrecirculated

Yufuin Onsen Glamping Kaze no Hibiki in Oita goes the same way, stating free-flowing water from its own source without heating or recirculation, and naming the spring type as simple alkaline.

The third is the interesting one. THE BASE GLAMPING ATAMI PREMIER in Shizuoka writes:

The source runs in the sixties Celsius, so it is partly diluted depending on season and weather

Writing down dilution looks like a disadvantage. But you cannot get into water at sixty degrees. Dilution there is not a drop in quality; it is what makes the bath usable. Written with its reason attached, it reads as candour instead.

Something that matters before free-flowing water

Free-flowing water is an easy value to understand, but when choosing a whole-house stay something else comes first.

Whether the bath is in your unit, or shared.

As counted in facilities belong to the unit, not the site, at glamping sites the facilities change from structure to structure within one property. Onsen works the same way: some units have their own, some send you to a bathhouse on the grounds. Of the 250, 114 carry an in-unit onsen tag and 41 a shared one. If you want to get in repeatedly through the night, that difference matters more than the spring type.

Then, if free-flowing water is your priority, one question covers it.

Learning the spring type before you leave

This last part is not practical advice so much as a small pleasure.

When you arrive, read the posting before you get in. The name of the source, the spring type, the temperature at which it emerges, whether it is diluted or heated. Sodium chloride spring, simple alkaline spring. Half of it will mean nothing to you.

Even so, knowing what you are sitting in changes the time in the bath a little. At Villa Metsä KARUIZAWA in Nagano or Private Villa Kagoshima Genkou no Mori in Kagoshima, simply having something to read while you soak adds one more step to the stay.

Not everything absent from a website is an unkindness. Some of it is just sitting somewhere else, waiting for you to arrive.

• At Pet-Friendly Glamping, 36% of the Units Take Dogs: Facilities Belong to the Unit, Not the Site
• When the Bath Is Outside the House: Whole-House Stays in an Onsen Town
• More Guests, Same One Bathroom: Counting Baths in a Whole-House Rental
• There Is No Toothbrush: Working Out What to Pack for a Whole-House Stay