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Manza Kogen Hotel

Water profile

Manza Kogen Hotel

Spring chemistry and what it does, with the research behind it.

万座温泉 6源泉混合泉Manza Onsen Six-Source Blend

酸AcidicHydrogen-Sodium-Magnesium Sulfate-Chloride spring · +含硫黄泉 · Sulfate · Chloride

Six of Manza's wells feed a mixing tank on the hotel grounds, and this certificate reads that blend: the Ubayu (yubatake) spring, three Oonigayu wells, Ryusen-no-yu and the Karaana source also known as Tsumatori-no-yu, all of them free-flowing. The result is an acidic, sulfur-bearing water at pH 2.1, sharp enough to prickle on contact, yellow at the outlet with yellow floc drifting in it and an unmistakable rotten-egg note of H₂S. Metasilicic acid runs to 205 mg/kg, laying a little silica smoothness over the acidic bite. The hotel's own onsen map documents the water for neuralgia, muscle and joint pain, cold sensitivity and fatigue recovery, and a companion panel explains that sulfur springs dissolve surface keratin while widening the capillaries.

Good for

Skin conditions

Sulfur and acidic waters are antibacterial and keratolytic, studied for atopic dermatitis and psoriasis.

atopic skin, eczema

Circulation

Skin-absorbed CO₂ and hydrogen sulfide relax the vessel walls; carbon-dioxide springs can raise peripheral blood flow several-fold.

tired legs

Aches & joints

Warmth eases stiffness and raises the pain threshold. Radon and sulfate springs show the strongest evidence for joint and muscle pain.

stiff shoulders

On the certificate:NeuralgiaMuscle painJoint pain

Warming

Salt forms a film on the skin that slows heat loss, so the warmth lingers long after the bath (the classic heat-keeping water, netto 熱の湯).

cold sensitivity

On the certificate:Cold sensitivity

Smooth skin

Bicarbonate and alkalinity gently lift dead keratin while silica hydrates, leaving skin smooth. This is the basis of the beautifying-water (bijin-no-yu 美人の湯) reputation.

dry, rough skin

Cuts

Mineral-rich chloride, sulfate and sulfur waters have a long-recorded soothing effect on minor cuts and slow-healing skin.

minor wounds

Recovery

Warmth and buoyancy lower stress markers and improve sleep; habitual bathing is linked to lower rates of depression.

fatigue, stress

On the certificate:Fatigue recovery

Take care

Sensitive-skin caution

Strongly acidic or sulfur-rich water can sting broken, atopic-flare, or dry elderly skin. Ease in slowly and rinse off if it stings.

broken or dry skin

Full composition

The bar is each ion's share of charge (mval%) within its group; over 20% names the spring. Gases, silica and trace metals are measured by mass only.

Cationsshare of charge (mval%)
  • Hydrogen8.7mgP85 national
  • Sodium189mgP48 national
  • Magnesium73.8mgP89 national
  • Aluminum24.3mgP93 national
  • Calcium41.3mgP54 national
  • Potassium40.5mgP82 national
  • Iron (II)6.9mgP85 national
  • Manganese5.5mgP97 national
Anionsshare of charge (mval%)
  • Sulfate959mgP95 national
  • Chloride225mgP59 national
  • HSO4281mgP86 national
  • Fluoride2.9mgP65 national
Non-dissociatedmeasured by mass
  • Metasilicic acid205mgP86 national
  • Metaboric acid15.5mgP69 national
  • H2SO4Free6.2mgP87 national
Dissolved gasesmeasured by mass
  • Free hydrogen sulfide65.7mgP99 national
  • Free carbon dioxide51.3mgP68 national
Trace metalsmeasured by mass
  • Arsenic0.30mgP88 national
  • CopperNDmg
  • MercuryNDmg
  • LeadNDmg

Measured at the source

pH
2.10
Acidic
Source temperature
62.0°C
Hot
Tonicity
2.08g/kg
Hypotonic
Free CO₂
51mg/kg
Low
Free H₂S
66mg/kg
Very high

On the certificate

  • Musculoskeletal disorders

Evidence

  1. Maeda M. 温泉の医学的効果とその科学的根拠. J. Hot Spring Science 70:197–207, 2021.
  2. Kario K et al. Hemodynamic Effects of Hot Spring Bathing. Hypertension Research 46(3):711–720, 2023.
  3. Tei C, Kihara T. Waon Therapy for Chronic Heart Failure. J. Cardiology 53(2):214–218, 2009.
  4. Coavoy-Sánchez SA et al. Hydrogen sulfide and dermatological diseases. Int. J. Dermatology, 2019.
  5. Naito Y et al. A Hot-Spring Water Improves Inflammatory Conditions in an Atopic Dermatitis Model. Biomedicines 13(11):2707, 2025.
  6. Akiyama H et al. Antimicrobial effects of acidic hot-spring water on S. aureus. J. Dermatological Science 24(3):193–200, 2000.
  7. Toriyama T et al. Carbon dioxide foot bathing on critical limb ischemia. International Angiology 21(4):367–373, 2002.
  8. Donaubauer AJ et al. Serial radon spa therapy on pain in musculoskeletal disorders. Frontiers in Immunology, 2024.
  9. Verhagen AP et al. Balneotherapy for rheumatoid arthritis. Cochrane Database of Systematic Reviews CD000518, 2015.
  10. Li H et al. Bicarbonate Ionized Water Bathing Enhances Natural Killer Cell Activity. Scientific Reports 14:51851, 2024.
  11. Takeda M et al. Hot spring bathing practices have a positive effect on mental health in Japan. Heliyon 9(9):e19631, 2023.
  12. Ministry of the Environment, Japan. 禁忌症及び入浴又は飲用上の注意事項 (2014 notice).official

姥湯Ubayu Spring

酸Acidic

Ubayu is piped from Manza's yubatake steam field, and the hotel's panel calls it the highest-yielding source in the whole of Manza. It is an acidic sulfur water at about pH 2.4 that clouds to a light milky white on contact with the air, and at roughly 73 °C the wellhead ranks among Japan's hottest natural sources. It fills the Suisho and Sawarabi tubs of the Sekitei open-air bath and the indoor tub of Hyakusen-no-yu; the same panel notes that the acidity is antibacterial and lifts old keratin, so skin comes out smooth.

Good for

Skin conditions

Sulfur and acidic waters are antibacterial and keratolytic, studied for atopic dermatitis and psoriasis.

atopic skin, eczema

Circulation

Skin-absorbed CO₂ and hydrogen sulfide relax the vessel walls; carbon-dioxide springs can raise peripheral blood flow several-fold.

tired legs

Aches & joints

Warmth eases stiffness and raises the pain threshold. Radon and sulfate springs show the strongest evidence for joint and muscle pain.

stiff shoulders

Warming

Salt forms a film on the skin that slows heat loss, so the warmth lingers long after the bath (the classic heat-keeping water, netto 熱の湯).

cold sensitivity

Smooth skin

Bicarbonate and alkalinity gently lift dead keratin while silica hydrates, leaving skin smooth. This is the basis of the beautifying-water (bijin-no-yu 美人の湯) reputation.

dry, rough skin

Cuts

Mineral-rich chloride, sulfate and sulfur waters have a long-recorded soothing effect on minor cuts and slow-healing skin.

minor wounds

Recovery

Warmth and buoyancy lower stress markers and improve sleep; habitual bathing is linked to lower rates of depression.

fatigue, stress

Take care

Sensitive-skin caution

Strongly acidic or sulfur-rich water can sting broken, atopic-flare, or dry elderly skin. Ease in slowly and rinse off if it stings.

broken or dry skin

Measured at the source

Source temperature
73.0°C
Hot
Tonicity
Hypotonic

Evidence

  1. Maeda M. 温泉の医学的効果とその科学的根拠. J. Hot Spring Science 70:197–207, 2021.
  2. Kario K et al. Hemodynamic Effects of Hot Spring Bathing. Hypertension Research 46(3):711–720, 2023.
  3. Tei C, Kihara T. Waon Therapy for Chronic Heart Failure. J. Cardiology 53(2):214–218, 2009.
  4. Coavoy-Sánchez SA et al. Hydrogen sulfide and dermatological diseases. Int. J. Dermatology, 2019.
  5. Naito Y et al. A Hot-Spring Water Improves Inflammatory Conditions in an Atopic Dermatitis Model. Biomedicines 13(11):2707, 2025.
  6. Akiyama H et al. Antimicrobial effects of acidic hot-spring water on S. aureus. J. Dermatological Science 24(3):193–200, 2000.
  7. Toriyama T et al. Carbon dioxide foot bathing on critical limb ischemia. International Angiology 21(4):367–373, 2002.
  8. Donaubauer AJ et al. Serial radon spa therapy on pain in musculoskeletal disorders. Frontiers in Immunology, 2024.
  9. Verhagen AP et al. Balneotherapy for rheumatoid arthritis. Cochrane Database of Systematic Reviews CD000518, 2015.
  10. Li H et al. Bicarbonate Ionized Water Bathing Enhances Natural Killer Cell Activity. Scientific Reports 14:51851, 2024.
  11. Takeda M et al. Hot spring bathing practices have a positive effect on mental health in Japan. Heliyon 9(9):e19631, 2023.
  12. Ministry of the Environment, Japan. 禁忌症及び入浴又は飲用上の注意事項 (2014 notice).official

竜泉の湯Ryusen-no-yu Spring

酸Acidic

Ryusen-no-yu is drawn from a spring along the river that runs past the hotel, and its colour is the point: a yellow water that the in-house panels call one of the few of its kind anywhere in Japan and the only source of its type used in Manza Onsen, by this hotel alone. Chemically it is an acidic sulfur spring at pH 2.2, sharp enough to prickle, and at about 80 °C the wellhead sits among Japan's hottest. It feeds the Ryusen, Shirataki and Beni tubs in the Sekitei open-air bath and the outdoor tub of Hyakusen-no-yu.

Good for

Skin conditions

Sulfur and acidic waters are antibacterial and keratolytic, studied for atopic dermatitis and psoriasis.

atopic skin, eczema

Circulation

Skin-absorbed CO₂ and hydrogen sulfide relax the vessel walls; carbon-dioxide springs can raise peripheral blood flow several-fold.

tired legs

Aches & joints

Warmth eases stiffness and raises the pain threshold. Radon and sulfate springs show the strongest evidence for joint and muscle pain.

stiff shoulders

Warming

Salt forms a film on the skin that slows heat loss, so the warmth lingers long after the bath (the classic heat-keeping water, netto 熱の湯).

cold sensitivity

Smooth skin

Bicarbonate and alkalinity gently lift dead keratin while silica hydrates, leaving skin smooth. This is the basis of the beautifying-water (bijin-no-yu 美人の湯) reputation.

dry, rough skin

Cuts

Mineral-rich chloride, sulfate and sulfur waters have a long-recorded soothing effect on minor cuts and slow-healing skin.

minor wounds

Recovery

Warmth and buoyancy lower stress markers and improve sleep; habitual bathing is linked to lower rates of depression.

fatigue, stress

Take care

Sensitive-skin caution

Strongly acidic or sulfur-rich water can sting broken, atopic-flare, or dry elderly skin. Ease in slowly and rinse off if it stings.

broken or dry skin

Measured at the source

Source temperature
65.0°C
Hot
Tonicity
Hypotonic

Evidence

  1. Maeda M. 温泉の医学的効果とその科学的根拠. J. Hot Spring Science 70:197–207, 2021.
  2. Kario K et al. Hemodynamic Effects of Hot Spring Bathing. Hypertension Research 46(3):711–720, 2023.
  3. Tei C, Kihara T. Waon Therapy for Chronic Heart Failure. J. Cardiology 53(2):214–218, 2009.
  4. Coavoy-Sánchez SA et al. Hydrogen sulfide and dermatological diseases. Int. J. Dermatology, 2019.
  5. Naito Y et al. A Hot-Spring Water Improves Inflammatory Conditions in an Atopic Dermatitis Model. Biomedicines 13(11):2707, 2025.
  6. Akiyama H et al. Antimicrobial effects of acidic hot-spring water on S. aureus. J. Dermatological Science 24(3):193–200, 2000.
  7. Toriyama T et al. Carbon dioxide foot bathing on critical limb ischemia. International Angiology 21(4):367–373, 2002.
  8. Donaubauer AJ et al. Serial radon spa therapy on pain in musculoskeletal disorders. Frontiers in Immunology, 2024.
  9. Verhagen AP et al. Balneotherapy for rheumatoid arthritis. Cochrane Database of Systematic Reviews CD000518, 2015.
  10. Li H et al. Bicarbonate Ionized Water Bathing Enhances Natural Killer Cell Activity. Scientific Reports 14:51851, 2024.
  11. Takeda M et al. Hot spring bathing practices have a positive effect on mental health in Japan. Heliyon 9(9):e19631, 2023.
  12. Ministry of the Environment, Japan. 禁忌症及び入浴又は飲用上の注意事項 (2014 notice).official

大苦湯Oonigayu Spring

酸Acidic

Oonigayu is piped in from the direction of Manza Hotel Juraku, and the hotel's panels single it out for two things: a denser milky-white cloud than Ubayu, and a distinctly slippery, almost slick feel on the skin. It is an acidic sulfur water around pH 2, a sodium sulfate-chloride type carrying the hydrogen sulfide sub-designation, and at about 70 °C the wellhead counts among Japan's hottest. It fills the Kohaku tub of the Sekitei open-air bath, and the panel adds that the water is spoken of as good for high blood pressure and arteriosclerosis.

Good for

Skin conditions

Sulfur and acidic waters are antibacterial and keratolytic, studied for atopic dermatitis and psoriasis.

atopic skin, eczema

Circulation

Skin-absorbed CO₂ and hydrogen sulfide relax the vessel walls; carbon-dioxide springs can raise peripheral blood flow several-fold.

tired legs

Aches & joints

Warmth eases stiffness and raises the pain threshold. Radon and sulfate springs show the strongest evidence for joint and muscle pain.

stiff shoulders

Warming

Salt forms a film on the skin that slows heat loss, so the warmth lingers long after the bath (the classic heat-keeping water, netto 熱の湯).

cold sensitivity

Smooth skin

Bicarbonate and alkalinity gently lift dead keratin while silica hydrates, leaving skin smooth. This is the basis of the beautifying-water (bijin-no-yu 美人の湯) reputation.

dry, rough skin

Cuts

Mineral-rich chloride, sulfate and sulfur waters have a long-recorded soothing effect on minor cuts and slow-healing skin.

minor wounds

Recovery

Warmth and buoyancy lower stress markers and improve sleep; habitual bathing is linked to lower rates of depression.

fatigue, stress

Take care

Sensitive-skin caution

Strongly acidic or sulfur-rich water can sting broken, atopic-flare, or dry elderly skin. Ease in slowly and rinse off if it stings.

broken or dry skin

Measured at the source

Source temperature
70.0°C
Hot
Tonicity
Hypotonic

Evidence

  1. Maeda M. 温泉の医学的効果とその科学的根拠. J. Hot Spring Science 70:197–207, 2021.
  2. Kario K et al. Hemodynamic Effects of Hot Spring Bathing. Hypertension Research 46(3):711–720, 2023.
  3. Tei C, Kihara T. Waon Therapy for Chronic Heart Failure. J. Cardiology 53(2):214–218, 2009.
  4. Coavoy-Sánchez SA et al. Hydrogen sulfide and dermatological diseases. Int. J. Dermatology, 2019.
  5. Naito Y et al. A Hot-Spring Water Improves Inflammatory Conditions in an Atopic Dermatitis Model. Biomedicines 13(11):2707, 2025.
  6. Akiyama H et al. Antimicrobial effects of acidic hot-spring water on S. aureus. J. Dermatological Science 24(3):193–200, 2000.
  7. Toriyama T et al. Carbon dioxide foot bathing on critical limb ischemia. International Angiology 21(4):367–373, 2002.
  8. Donaubauer AJ et al. Serial radon spa therapy on pain in musculoskeletal disorders. Frontiers in Immunology, 2024.
  9. Verhagen AP et al. Balneotherapy for rheumatoid arthritis. Cochrane Database of Systematic Reviews CD000518, 2015.
  10. Li H et al. Bicarbonate Ionized Water Bathing Enhances Natural Killer Cell Activity. Scientific Reports 14:51851, 2024.
  11. Takeda M et al. Hot spring bathing practices have a positive effect on mental health in Japan. Heliyon 9(9):e19631, 2023.
  12. Ministry of the Environment, Japan. 禁忌症及び入浴又は飲用上の注意事項 (2014 notice).official

嬬取の湯Tsumatori-no-yu Spring

酸Acidic

Tsumatori-no-yu is the one clear water among the eight tubs of the Sekitei open-air bath. The panels explain why: it carries almost no sulfur or hydrogen sulfide, which leaves its acidity fully exposed at about pH 1.5, the strongest of the hotel's four sources and sharp enough to prickle noticeably on entry. It is an acidic magnesium-sodium sulfate-chloride water, and at roughly 90 °C the wellhead is among Japan's hottest. Its salt load is high enough that the hotel recommends bathing here last: the water holds heat long after you get out, and the panels credit it with an antiseptic effect, faster healing of small cuts and improved skin renewal.

Good for

Skin conditions

Sulfur and acidic waters are antibacterial and keratolytic, studied for atopic dermatitis and psoriasis.

atopic skin, eczema

Circulation

Skin-absorbed CO₂ and hydrogen sulfide relax the vessel walls; carbon-dioxide springs can raise peripheral blood flow several-fold.

tired legs

Aches & joints

Warmth eases stiffness and raises the pain threshold. Radon and sulfate springs show the strongest evidence for joint and muscle pain.

stiff shoulders

Warming

Salt forms a film on the skin that slows heat loss, so the warmth lingers long after the bath (the classic heat-keeping water, netto 熱の湯).

cold sensitivity

Smooth skin

Bicarbonate and alkalinity gently lift dead keratin while silica hydrates, leaving skin smooth. This is the basis of the beautifying-water (bijin-no-yu 美人の湯) reputation.

dry, rough skin

Cuts

Mineral-rich chloride, sulfate and sulfur waters have a long-recorded soothing effect on minor cuts and slow-healing skin.

minor wounds

Recovery

Warmth and buoyancy lower stress markers and improve sleep; habitual bathing is linked to lower rates of depression.

fatigue, stress

Take care

Sensitive-skin caution

Strongly acidic or sulfur-rich water can sting broken, atopic-flare, or dry elderly skin. Ease in slowly and rinse off if it stings.

broken or dry skin

Measured at the source

Source temperature
90.0°C
Hot
Tonicity
Hypotonic

Evidence

  1. Maeda M. 温泉の医学的効果とその科学的根拠. J. Hot Spring Science 70:197–207, 2021.
  2. Kario K et al. Hemodynamic Effects of Hot Spring Bathing. Hypertension Research 46(3):711–720, 2023.
  3. Tei C, Kihara T. Waon Therapy for Chronic Heart Failure. J. Cardiology 53(2):214–218, 2009.
  4. Coavoy-Sánchez SA et al. Hydrogen sulfide and dermatological diseases. Int. J. Dermatology, 2019.
  5. Naito Y et al. A Hot-Spring Water Improves Inflammatory Conditions in an Atopic Dermatitis Model. Biomedicines 13(11):2707, 2025.
  6. Akiyama H et al. Antimicrobial effects of acidic hot-spring water on S. aureus. J. Dermatological Science 24(3):193–200, 2000.
  7. Toriyama T et al. Carbon dioxide foot bathing on critical limb ischemia. International Angiology 21(4):367–373, 2002.
  8. Donaubauer AJ et al. Serial radon spa therapy on pain in musculoskeletal disorders. Frontiers in Immunology, 2024.
  9. Verhagen AP et al. Balneotherapy for rheumatoid arthritis. Cochrane Database of Systematic Reviews CD000518, 2015.
  10. Li H et al. Bicarbonate Ionized Water Bathing Enhances Natural Killer Cell Activity. Scientific Reports 14:51851, 2024.
  11. Takeda M et al. Hot spring bathing practices have a positive effect on mental health in Japan. Heliyon 9(9):e19631, 2023.
  12. Ministry of the Environment, Japan. 禁忌症及び入浴又は飲用上の注意事項 (2014 notice).official

鷹梓の湯Takaazusa-no-yu Spring

酸AcidicHydrogen Sulfate spring · +含硫黄泉 · Sulfate

A strongly acidic sulfur spring: at pH 2.0 the water prickles on contact, and at the wellhead it runs milky white with a pronounced rotten-egg note of hydrogen sulfide. Sulfate accounts for roughly four-fifths of the anion load and free H₂S reaches 104 mg/kg, while hydrogen ions make up almost half the cation balance, which is where the bite comes from. Metasilicic acid at 125 mg/kg lays a thin silica smoothness over that acidity.

Good for

Skin conditions

Sulfur and acidic waters are antibacterial and keratolytic, studied for atopic dermatitis and psoriasis.

atopic skin, eczema

Circulation

Skin-absorbed CO₂ and hydrogen sulfide relax the vessel walls; carbon-dioxide springs can raise peripheral blood flow several-fold.

tired legs

Aches & joints

Warmth eases stiffness and raises the pain threshold. Radon and sulfate springs show the strongest evidence for joint and muscle pain.

stiff shoulders

Smooth skin

Bicarbonate and alkalinity gently lift dead keratin while silica hydrates, leaving skin smooth. This is the basis of the beautifying-water (bijin-no-yu 美人の湯) reputation.

dry, rough skin

Cuts

Mineral-rich chloride, sulfate and sulfur waters have a long-recorded soothing effect on minor cuts and slow-healing skin.

minor wounds

Recovery

Warmth and buoyancy lower stress markers and improve sleep; habitual bathing is linked to lower rates of depression.

fatigue, stress

Take care

Sensitive-skin caution

Strongly acidic or sulfur-rich water can sting broken, atopic-flare, or dry elderly skin. Ease in slowly and rinse off if it stings.

broken or dry skin

Full composition

The bar is each ion's share of charge (mval%) within its group; over 20% names the spring. Gases, silica and trace metals are measured by mass only.

Cationsshare of charge (mval%)
  • Hydrogen10.7mgP93 national
  • Aluminum31.1mgP94 national
  • Sodium60.5mgP17 national
  • Magnesium29.3mgP76 national
  • Calcium30.8mgP46 national
  • Potassium18.7mgP61 national
  • Iron (II)11.6mgP90 national
  • Manganese2.3mgP92 national
Anionsshare of charge (mval%)
  • Sulfate788mgP94 national
  • HSO4285mgP87 national
  • Chloride63.9mgP30 national
  • Fluoride1.2mgP49 national
Non-dissociatedmeasured by mass
  • Metasilicic acid125mgP64 national
  • H2SO4Free7.7mgP89 national
  • Metaboric acid5.1mgP36 national
Dissolved gasesmeasured by mass
  • Free hydrogen sulfide104mgP99 national
  • Free carbon dioxide0.0000mg
Trace metalsmeasured by mass
  • Lead0.0060mgP29 national
  • ArsenicNDmg
  • CopperNDmg
  • MercuryNDmg

Measured at the source

pH
2.00
Acidic
Source temperature
49.0°C
Hot
Tonicity
1.47g/kg
Hypotonic
Flow rate
10L/min
Low
Free H₂S
104mg/kg
Very high

Evidence

  1. Maeda M. 温泉の医学的効果とその科学的根拠. J. Hot Spring Science 70:197–207, 2021.
  2. Tei C, Kihara T. Waon Therapy for Chronic Heart Failure. J. Cardiology 53(2):214–218, 2009.
  3. Coavoy-Sánchez SA et al. Hydrogen sulfide and dermatological diseases. Int. J. Dermatology, 2019.
  4. Naito Y et al. A Hot-Spring Water Improves Inflammatory Conditions in an Atopic Dermatitis Model. Biomedicines 13(11):2707, 2025.
  5. Akiyama H et al. Antimicrobial effects of acidic hot-spring water on S. aureus. J. Dermatological Science 24(3):193–200, 2000.
  6. Toriyama T et al. Carbon dioxide foot bathing on critical limb ischemia. International Angiology 21(4):367–373, 2002.
  7. Donaubauer AJ et al. Serial radon spa therapy on pain in musculoskeletal disorders. Frontiers in Immunology, 2024.
  8. Verhagen AP et al. Balneotherapy for rheumatoid arthritis. Cochrane Database of Systematic Reviews CD000518, 2015.
  9. Li H et al. Bicarbonate Ionized Water Bathing Enhances Natural Killer Cell Activity. Scientific Reports 14:51851, 2024.
  10. Takeda M et al. Hot spring bathing practices have a positive effect on mental health in Japan. Heliyon 9(9):e19631, 2023.
  11. Ministry of the Environment, Japan. 禁忌症及び入浴又は飲用上の注意事項 (2014 notice).official

Educational, not medical advice. If you have a health condition, consult a physician before onsen therapy.