How does reverse osmosis actually work?

#236 When a retired chemist wrote in… we had to explore to his great questions. How does reverse osmosis actually work? Should you put aluminum foil in your dishwasher? Why do mixed powders mysteriously un-mix themselves? This episode is full of clever questions, surprising chemistry, and very strong contributions from listener Vince! Support this podcast on Patreon Buy Podcast Merch and Apparel Check out our website at chemforyourlife.com Watch our episodes on YouTube Find us on Instagram, Twitter, and Facebook @ChemForYourLife Timestamps 0:00 – Intro + listener Vince brings the chemistry 1:30 – Reverse osmosis: what it is and why it works 2:00 – Osmosis explained simply 3:35 – Reverse osmosis vs normal filtration 4:20 – What reverse osmosis removes (PFAS, salt, contaminants) 5:00 – Why “pure” water can create new problems 6:10 – Why some companies re-mineralize water 8:10 – Water kiosks, PFAS, and an unexpected lead problem 10:40 – Why reverse osmosis creates so much wastewater 11:40 – Should you put aluminum foil in your dishwasher? 13:00 – Why dishwashers are secretly chemical reactors 16:00 – Melissa’s theories on what the foil might be doing 17:00 – Aluminum, silver tarnish, and stainless steel 21:10 – Sacrificial metals: aluminum protecting steel 24:20 – Dishwasher complaints + real life testing plans 26:20 – Why powders and solids can “un-mix” themselves 27:45 – The Brazil Nut Effect explained 29:20 – Why mixed particle sizes matter 30:40 – Instant coffee jars, Raisin Bran, and product design 31:30 – Mark Rober, floating in sand, and weird physics/chemistry crossover 33:40 – Bird tangent: woodcocks stomping for worms 35:15 – Wrap-up + thanks to Vince and the Chemmunity Support this podcast on Patreon Buy Podcast Merch and Apparel Check out our website at chemforyourlife.com Watch our episodes on YouTube Find us on Instagram, Twitter, and Facebook @ChemForYourLife References from the Episode: https://www.acs.org/pressroom/presspacs/2026/february/elevated-lead-levels-could-flow-from-some-us-drinking-water-kiosks.html https://www.epa.gov/watersense/point-use-reverse-osmosis-systems https://pubs.acs.org/doi/10.1021/acs.est.9b01755 https://pubs.acs.org/doi/10.1021/es60115a011 https://www.tasteofhome.com/article/aluminum-foil-in-dishwasher/ https://www.nature.com/articles/s41598-021-87280-1 https://www.sciencedirect.com/science/article/pii/S0032591010004547 https://www.scientificamerican.com/article/why-does-shaking-a-can-of/ https://www.sciencedirect.com/science/article/pii/ S2666330923000250#:~:text=Introduction,corrosion%20in%20an%20aqueous%20environment. https://pubs.acs.org/doi/full/10.1021/acsami.3c08922 https://chem.libretexts.org/Courses/University_of_British_Columbia/CHEM_100%3A_Foundations_of_Chemistry/14%3A_Acids_and_Bases/14.05%3A_Reactions_of_Acids_and_Bases https://www.compoundchem.com/2018/05/23/dishwashers/ Thanks to our monthly supporters Kelly D. Bri Summer Alden Amanda Raymond Kyle McCray Justine Ash Vince W Julie S. Heather Ragusa Autoclave Dorien VD Scott Beyer Jessie Reder J0HNTR0Y Jeannette Napoleon Cullyn R Erica Bee Elizabeth P Rachel Reina Letila Katrina Barnum-Huckins Suzanne Phillips Venus Rebholz Jacob Taber Brian Kimball Kristina Gotfredsen Timothy Parker Steven Boyles Chris Skupien Chelsea B Avishai Barnoy Hunter Reardon Support this podcast on Patreon Buy Podcast Merch and Apparel Check out our website at chemforyourlife.com Watch our episodes on YouTube Find us on Instagram, Twitter, and Facebook @ChemForYourLife