2 HN users recommended this explainer2 months2015–2025score 2
Years with an HN recommendation, 2007–2026
HN commenters treat it as the standard short answer whenever UK taps come up.
Tom Scott explains why Britain historically has separate hot and cold taps rather than mixer taps, tracing it to how water was stored in tanks. He notes why the hot tap is not safe to drink from.
“Short video by Tom Scott on the subject for those interested.” (HN, 2021)
It makes a lot of sense having them separate. Tom Scott explains [this video] Here in California showers and much other plumbing are required to have backflow valves so that hot and cold don't cross contaminate.
Short video by Tom Scott on the subject for those interested. [this video] tldw; Older homes in the UK had a water storage tank in the roof space that fed the water heating tank. This couldn't be classified as drinking water so wasn't allowed to be combined with the safe mains water that fed the cold tap. These days modern houses mostly use combi-boilers with no storage tank, so mostly both hot and cold are drinkable and it's not an issue. But preferences still lean towards the separate taps.
Short explanation of UK water storage tanks and separate taps
On the topic of mixer-taps in bathrooms, the UK typically has separate taps due to the way the water is stored, or used to be stored: [this video] I was pleased when I remodelled my bathroom there and installed a mixer. So much more convenient.
Explains UK separate taps from water storage history
Hot water heaters frequently have sacrificial anode rods to prevent corrosion. The rods corrode over time and dissolve into the water. Lower cost aluminum rods have health concerns, not as much with magnesium rods. See also Tom Scott's video on Britain's history with separate hot and cold taps and why hot taps sometimes had unsanitary cold water tanks to supply them: [this video]
History of UK separate taps and unsanitary cold water tanks
Mandatory Giphy: [link] Also mandatory explanation why UK historically has had 2 taps: [this video] Which in the end is understandable. It's outdated. What isn't understandable is having the light switch OUTSIDE of the friggin' restroom.
Explanation of why the UK historically has two taps
That's because it is primarily a historical artifact[0]. Most modern plumbing heats water on-demand, which pretty much entirely avoids the risk of storage tank contamination or Legionella. [0]: [this video]
Source for historical reasons behind separate taps
Video list and Hacker News comment labels from HackerTube (prompted by @karpathy), released under ODC-By 1.0, built on the open-index/hacker-news archive. Hacker News data is provided by Y Combinator; comments remain the work of their authors. Video titles, channel names and thumbnails belong to their creators and are shown via YouTube. HackerTube Watch is an unofficial edition. Data export of 2026-10-31.
Plays via YouTube's privacy-enhanced embed
8 Hacker News comments
From the HN archive; up to 20 kept per video, favoring different commenters. Recommendations first.
Citations, criticism and jokes