Why Britain Uses Separate Hot and Cold Taps
Tom Scott2 HN recommenders · recommended in 2 months, 2015–2025
explainer · general · evergreen · 2015–2025 on HN
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.
HN commenters treat it as the standard short answer whenever UK taps come up.
Up next
11 mo on HNRepublic, Lost | Lawrence Lessig | Talks at Google
Talks at Google
10 HN recommender · 2011–2017
5 mo on HNPenn and Teller on Vaccinations
UltraMiraculous
6 HN recommender · 2013–2018
3 mo on HNVintage Electronics - The Tefifon
Techmoan
3 HN recommender · 2016–2018
2 mo on HNDeath to Pennies
CGP Grey
2 HN recommender · 2012–2023
12 mo on HNDetergent packs are kinda wishy-washy (Dishwashers Explained)
Technology Connections
15 HN recommender · 2021–2025
8 mo on HNBuilding a realistic artificial sun (for dark winter days)
DIY Perks
9 HN recommender · 2020–2025
8 mo on HNI messed up. You're using too much detergent.
Technology Connections
10 HN recommender · 2021–2025
5 mo on HNYour dishwasher is better than you think (tips, tricks, and how they work)
Technology Connections
6 HN recommender · 2024–2026
4 mo on HNBest fan placement to move air through the house
Matthias random stuff
4 HN recommender · 2021–2025
4 mo on HNMaking Infrared Cooling Paint From Grocery Store Items (w/Novel CaCO₃ Microsphere Synthesis)
NightHawkInLight
5 HN recommender · 2023–2026
4 mo on HNWhy Air Quality Matters
David Heinemeier Hansson
3 HN recommender · 2018–2024
4 mo on HNPrimitive Technology: Tiled Roof Hut
Primitive Technology
3 HN recommender · 2015–2018
8 comments from Hacker News
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.
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.
Obligatory Tom Scott video on the topic: * link Bonus: "Why Britain Uses Separate Hot and Cold Taps": * ▶ this video
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
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.
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
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.
At least in Britain, if there are separate taps for hot and cold, you shouldn't trust drinking from the hot tap: ▶ this video