Boukai

民宿 望海みんしゅく ぼうかい

Lodging
Kansai·Wakayama

Day Use

Yes

Bathing & Water

OnsenYes

Uses natural hot spring water

甘露の湯

Kanro-no-yu Spring

Operated by · 新湯崎温泉供給株式会社

Sampled at wellhead
Bicarbonate
+ Chloride
Classification

Sodium Bicarbonate-Chloride spring

A sodium-led bicarbonate-chloride spring — the soft 'jūsō-sen' style with a salty edge from a chloride sub-type. Neutral in pH and gentle on the skin, it sits within Japan's beauty-water family. The source emerges above 86 °C, placing it among Japan's hottest natural sources, and carries a faint hydrogen sulfide note with a slightly salty tang at the wellhead. A generous 107.7 mg/kg of metasilicic acid leaves a thin silica film that makes skin feel noticeably smoother.

pH
7.40
Neutral
Source temperature
86.3°C
Hot
Tonicity
5.50g/kg
Hypotonic
Flow rate
355L/min
Typical
Free H₂S
0.20mg/kg
Low
Color
colorless and transparent
Taste
slightly salty
Odor
faint hydrogen sulfide
Highlights
  • High silica
  • Top-decile hot

Analyzed Jan 18, 2024·一般社団法人 和歌山県薬剤師会 医薬品・公衆衛生検査センター·Cert no. 第E2401144号

Programs

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SM
Sergey M
4 months ago

677. Boukai, Shirahama, Wakayama Visited for higaeri for 660. Higaeri hours are 14:00-19:00. They sell the Wakayama 12 Onsen stamp book. Indoor bath with clear water, temperature around 47.8. There's cold water and tools to dilute it - brought it down to 43 quickly. A bit stuffy inside. 09.11.2025