Ask A Geoscientist: What’s With This Eggy Water?

Tap water in Iceland: pure, refreshing and—as they often say about the best things in life—it comes for free. Why, then, does this source of Icelandic pride (and hydration) leave so many newcomers and tourists flabbergasted the first time they come to Reykjavík and take a shower?

The harsh, sulphuric smell—which locals barely even notice—comes up every time you turn on the hot tap. I heard a rumour that the sulphur is added to the water artificially, so I asked Bergur Sigfússon from the research team at Reykjavík Energy to clear this up for me.

Our team braving the sulphuric steam around Nesjavellir

“The hot water is derived from two distinct sources: from low-temperature areas (Laugarnes, Elliðaárdalur, Reykir and Reykjahlíð) on the one hand, and from high-temperature geothermal power plants located in Nesjavellir and Hellisheiði on the other,” he explains. “The hot water from the low-temperature areas comes from deep boreholes which naturally contain sulphur of various concentrations. Prior to being distributed, the geothermal water is stored and mixed in reservoir tanks (such as the ones in Perlan).”

“In case of the hot water coming from the high-temperature power plants, a small amount of geothermal steam is injected at the end of the heating process of the cold groundwater,” he continues, summing up that—in both cases—a small excess of hydrogen sulphide (the cause of the smell) is needed to ensure a complete removal of oxygen from the water. This is a necessary preventive measure against corrosion in the pipes and radiators of local homes and businesses.

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