MythBusters · Video summary

Can Metals In A Bathtub Create A Massive Explosion? | MythBusters

In this episode of MythBusters, the team investigates whether adding alkaline metals like rubidium and cesium to water can create a hand grenade-sized explosion in a toilet, ultimately concluding that while the reactions are impressive, they do not match the explosive claims and are busted. They then conduct a dramatic experiment with sodium and potassium, which also fails to produce a significant explosion, reinforcing that such myths are often exaggerated online.

MythBusters · June 8, 2026 · 21-min episode · 5-min read

Can Metals In A Bathtub Create A Massive Explosion? | MythBusters

Key takeaways

Alkaline metals like rubidium and cesium do not create hand grenade-sized explosions when added to water, as claimed in some internet videos.
The reactions of alkaline metals with water produce hydrogen gas and heat, but the results are not comparable to high explosives like TNT.
The MythBusters team used 25 grams of rubidium, more than 10 times the amount suggested in the myth, but still observed only a geyser effect rather than an explosion.
While sodium and potassium produced exciting reactions, they still did not result in an explosion comparable to a C4 detonation, which is significantly more powerful.
The myth that a burning piano could explode was also busted, as the tension in the strings would release gradually rather than explosively.
Research the chemical properties and reactions of alkaline metals to understand their behavior in water before attempting any experiments.

Chapters

0:00🔍 Introduction to the Myth
2:00💣 Explosive Comparisons
4:00🚽 Toilet Explosion Setup
5:00💥 Toilet Explosion
6:00⚗️ Rubidium Reaction
7:00💨 Cesium Reaction
8:00❌ Myth Busted
9:00🔥 Sodium Explosion Attempt
10:00💥 Sodium Reaction Results
11:00🎆 Potassium Test
12:00🔍 Conclusion on Alkali Metals
14:00🎹 Piano Explosion Myth Introduction
15:00🔥 Preparing the Piano
16:00💥 Piano Burn Test
18:00❌ Piano Myth Busted
19:00💣 Exploding Piano with C4
20:00🎉 Final Explosion
21:00📝 Final Thoughts

The digest

High-Level Overview

This episode of MythBusters investigates the viral internet claim that dropping small amounts of highly reactive alkali metals—such as rubidium and cesium—into water (specifically in a bathtub or toilet) can cause a massive, hand grenade-sized explosion capable of destroying bathroom fixtures. The team conducts controlled experiments, comparing these chemical reactions to actual explosive detonations. Additionally, the episode examines the separate myth that a burning piano can explode due to the tension in its strings. Both myths are tested and analyzed with a combination of scientific explanation, large-scale experiments, and safety precautions. The results definitively bust both claims, clarifying common misconceptions about chemical reactivity and physical tension in everyday materials.