hot springs and sulphur: what’s that smell?

If you’ve spent time exploring true geothermal hot springs — the kind that deliver very hot mineral water from deep underground — you’re most likely familiar with a certain distinct scent. Some describe this scent as ‘pungent’, while others would say it smells ‘gaseous’. Either way, this scent has an entirely natural source: sulphur.

what is sulphur and how does it relate to hot springs?

Sulphur is a non-toxic mineral element found in the Earth’s crust and, interestingly, in certain meteorites. It is believed that prehistoric humans used sulphur in cave paintings and as a health tonic. It’s often present in areas with volcanic activity and mineral hot springs.

As geothermal water travels away from the Earth’s mantle and towards the Earth’s surface, it dissolves mineral deposits found in rocks and soil and brings remnants of these minerals with it. When this mineral-rich water meets oxygen, it releases the trademark sulphur smell.

This scent will be stronger if the water originates from quite deep underground (because it will collect more minerals along the way) and if it’s very hot (as hotter water dissolves minerals more efficiently).

why is the sulphur smell stronger around certain pools?

As Peninsula Hot Springs comes from true mineral springs, the water that flows into our pools is rich in a range of minerals — including sulphur. Most of our pools also contain trace amounts of chlorine in order to maintain stringent standards of hygiene, and this tends to neutralise the sulphur scent.

Our indoor Private Baths and our Bathing Barrels, however, are filled with pure mineral water — and therefore carry a stronger sulphur smell. As private bathing experiences that are drained and refilled following each session, these baths require no chlorine.

The same is true of the Mineral Showers that can be found throughout the bathing areas: since the water drains away from the showers following each use, they flow with pure, chlorine-free mineral water.

This means that our Private Baths and Bathing Barrels are especially suitable for anyone who is particularly sensitive to chlorine. And while the smell of sulphur can be powerful at first, guests usually find that the strength of the scent starts to dissipate after a short time on the premises. The amount of sulphur found in our hot springs is also completely harmless.

what other minerals are found in Peninsula Hot Springs pools?

While sulphur is a mineral found in almost all true mineral springs, the precise mineral content of hot spring pools differs depending on their unique location.

Peninsula Hot Springs is located on the Mornington Peninsula’s Selwyn fault line, and our water flows from 637 metres underground. Our pools are filled from a filtration hot spring with surface water believed to be more than 10,000 years old.

This water is rich in beneficial minerals.

our springs contain:

Boron. Boron builds muscle mass, increases brain activity and strengthens bones.

Magnesium. Magnesium converts blood sugar to energy and promotes healthy skin.

Potassium. Potassium assists in the normalisation of heart rhythms, assists in reducing high blood pressure, helps to eliminate body toxins and promotes healthy skin.

Chloride. Mineral springs naturally rich in chlorides — meaning they contain between 0.5 and 3 percent — are considered by some researchers to be beneficial for rheumatic conditions, arthritis, central nervous system conditions and post-traumatic and post-operative disorders.

Bicarbonate. Bathing in bicarbonate water assists in opening peripheral blood vessels and improving circulation to the body's extremities. It may also help to address hypertension and mild atherosclerosis. Some researchers believe that bicarbonate baths assist cardiovascular disease and nervous system imbalances.

So there you have it: the curious scent of true hot springs demystified. If you’d like to learn more about our water, feel free to approach a member of our friendly Pools team next time you’re bathing in our springs.