The sulfuric smell in the hot water has nothing to do with the use of geothermal power. Most tourists think so because they've only been to or near the capital area.

Reykjavík artificially adds sulfur to its hot water to reduce the corrosion of their hot water pipes.

I can't find a source for that in English but there's one in Icelandic, it's the "Vinnslutæknileg vandamál við vinnslu jarðhita" section.

1. http://web.archive.org/web/20160813045634/http://www.samorka...