2704: Faucet

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It's okay, they can figure out which control positions produce scalding water via a trial-and-error feedback loop with a barely-perceptible 10-second lag.
Title text: It's okay, they can figure out which control positions produce scalding water via a trial-and-error feedback loop with a barely-perceptible 10-second lag.


A variety of faucet controls have been designed for the control of a shower or sink's water output; however, Randall seems to find all the existing options to be inadequate in some way and posits in this comic that designers share a desire to create a more ideal design. The comic shows one such designer, looking unkempt and rambling like a madman as he explains to an off-screen character how his new faucet design works. The off-screen character promptly tells him that he should get some sleep, a request which the designer ignores in favor of continuing the search for the "perfect" water faucet.

In general, a faucet's output has two independent parameters: flow velocity and temperature; some particularly frustrating faucet controls only offer one degree of freedom which simultaneously turns up the flow rate and the temperature, and thus cannot fully explore the shower-space (making it sometimes difficult to find a comfortable setting). Some faucets can adjust both parameters but only have a single lever which must be angled along degrees of freedom which are not always labeled clearly or intuitively, and this may also irk Randall. Other faucets have two independent controls for the flow of cold water and hot water; however, while these are highly granular, it can be difficult to adjust the parameters independently e.g. change the temperature without changing the flow, or changing the flow without changing the temperature.

While two-handle faucets may seem simple in the abstract, they are imperfect in practice. In older houses or those with hot water systems based on tankless or instant hot water heaters, the hot water pressure is rarely the same as the cold water pressure. This can cause problems with cold water flowing back into the hot line, creating temperature drifts, unexpected changes in temperature based on slight input changes, and non-reproducibility in shower settings.

Newer systems include thermostatic mixing valves which are designed to alleviate these problems; ideally, they contain one control for temperature and one for flow, which would seem to fit the "non-confusing" brief and solve Randall's problems. However, designing a system technically functional and making it intuitive (and making it work in practice for all water supply systems) is non-trivial, so Randall may have had trouble with even these faucets in the past.

The experience of a shower being affected by a significant change in usage of water elsewhere in the building (a running washing machine clicking into or out of a rinse-cycle, or the sudden use of a flush-toilet) is a typical one in any place without deliberately over-engineered plumbing. Purpose built hotels may have an in-built degree of resilience of this kind, but over many temporary stay-overs by guests (each new set having to become familiar with the plumbing) will develop wear and tear that later guests will not be automatically aware of — including the gradual wearing off of the traditional red and blue arrows intended to show the polarity of hot-and-cold controls.

The title text is a hyperbolic and slightly sarcastic explanation of the merits of a faucet system, presumably from its designer. It describes that the user can identify an undesirable result, e.g. of scalding water, through a trial-and-error feedback loop. But, with a decidedly long delay in response time as the scalding (then non-scalding) mix works its way through the system, it means that they are left waiting for any adjustments made to prove themselves as useful (or not) whilst still experiencing the prior state of the water.


[A designer with short, messy hair and a scuffed face stands in front of a whiteboard. He is holding a pen and is sketching with it above his head. His other empty hand is also held up above his head, possibly touching part of the sketch. On the whiteboard are various scribbles, pieces of illegible text, drawings of waves, arrows, and side views and cross sections of a faucet. In the center of the whiteboard, drawn with soft, sketched lines is the faucet, the designers empty hand is touching it. It has a vertical wall-mounted square base with a semicircle above. Attached to the semicircle is a tightly curled helical tube that curls twice, this is the one the designer is drawing on at the moment. Below it is a drawing of a spout with a stream of water going almost to the bottom of the board. On the floor around the designers feet is an upright beverage can, a large piece of crumpled paper, and 6 smaller pieces of crumpled or ripped paper and one larger flat piece of paper. He talks to someone off-panel, who replies from a star burst on the right border of the panel.]
Designer: ...So you tighten the spiral to make the water hotter, and to adjust the flow rate you just-
Off panel voice: You need to sleep.
Designer: No! I can do this!
[Caption below the panel:]
Every designer's dream is to finally invent a non-confusing faucet control.

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Are faucet designs considered to be confusing? I'm never confused by normal ones like these -- Flekkie (talk) 02:12, 29 November 2022 (please sign your comments with ~~~~)

Yeah I came here wondering the same thing. Is the joke perhaps not so much that the controls are confusing in terms of intent, but just in terms of determining the bounds? Eg, with two identical faucet controls and identical water pressures, "full blast hot" still translates to something radically different, if one building has a water heater set to 120F and the other building has a water heater set to 160F. (talk) 02:46, 29 November 2022 (please sign your comments with ~~~~)
(I find °F confusing, personally, but...) ...the easiest thing is to have two taps, one hot and one cold. Yes, they can combine into a single spout, but there are various conflicting plusses and minuses of that over having the two independent ones per outlet. Speaking (as I'm sure mixer-tap afficionados worldwide will appreciate) as a Brit. 03:03, 29 November 2022 (UTC)
Relevant Tom Scott video: Why Britain Uses Separate Hot and Cold Taps. TL;DR: British houses used to get their hot water from rat-filled cisterns so they wanted to keep the hot water separate from the cold water, and old habits die hard. 03:34, 29 November 2022 (UTC)
Silliness of dual-taps aside, that doesn't solve the issue of identical tap hardware yielding radically different results depending on what the hot water thermostat is set to. Maybe that's not the original joke (I'm still not sure what it was) but it's worth mentioning at least. 03:39, 29 November 2022 (UTC)
I don't think those are confusing, but in many cases the feedback is too slow (e.g. due to the water in the pipes coming from the hot water source having cooled since the tap was last used), or inconvenient (e.g. the pressure of the hot water not being enough to trigger on-demand gas heaters). While theoretically that design allows exploring the whole temperature/pressure space, in practice one needs some trial-and-error and delay to find the correct setting (as Randall points out in the title text) to make it work. --Waldir (talk) 10:54, 29 November 2022 (UTC)
It's really a joke we are too European to understand. Visit the US to see faucet control disasters in all their glory. 10:56, 29 November 2022 (UTC)
Yeah, here in Europe I've seen faucets with mechanical thermostats to regulate the temperature and therefore two dials for either flow or temperature. This was more than 20 years ago. --Sarsey (talk) 12:01, 29 November 2022 (UTC)
Funny, the absolute worst faucet I experienced was in this fall in England (which is part of Europe for some definitions but not others). The temperature selection knob had 180° ambiguity---especially for my poor vision when uncorrected---and no barrier between maximum hot and maximum cold. So, I spent a shower thinking I was operating at mid-range and wondering why there seemed to be no middle ground between freezing cold and scalding hot. Fortunately had an epiphany while exploring the town. Philhower (talk) 14:13, 29 November 2022 (UTC)
What's hot and what's cold? Do you turn it in the direction of the red to increase the temperature, or do you turn it so that you can see more of the red than the blue to increase the temperature? Taps exist that follow either convention. In the first case, you turn it to the left, while in the second you turn it to the right. That kind of tap is far more confusing than the traditional one with two knobs (though I've also seen a tap with knobs having "chaud" and "froid" on them in a country where French is not an official language without anything else to distinguish them, so I guess even that is not so straight-forward). 21:12, 29 November 2022 (UTC)
The design that Flekkie showed has 2 directions of freedom: left-right, and up-down. Left and right is temperature, and isn't "turning" as much as "tilting" in that direction. The effective space is U-shaped. The default position you see is no water. Tilt straight back and you get lukewarm full-pressure water. The back right position is cold full-pressure water. The back left position is hot full-pressure water. To get any other pressure or temperature, just tilt somewhere within that U to get what you need (though very few people do, and just use the 4 positions). Admiral Memo (talk) 19:28, 2 December 2022 (UTC)

I sympathize with Randall here; even controls designed to independently control temperature and flow rarely meet both the "intuitive to use at a glance" and "function as described" requirements to make them non-confusing. Dextrous Fred (talk) 03:44, 29 November 2022 (UTC)

Wouldn't it be super simple to just have a slider that goes from hot to cold, and a second one that goes from slow to fast flow? Or one for hot, one for cold, with the higher the slider goes, the more the flow is increased? I don't see how much simpler you can get it. Hell, you could even use a dial for temperature (all dials turn clockwise to increase) with a digital readout. 05:25, 29 November 2022 (UTC)

I suppose the issue with that is that, unlike simple mixer taps that control the flow of hot and cold water independently, relying on the human to find the right mixture that creates the desired flow and temperature, what you're describing requires a more complex system that is able to do that process automatically, so it can't be a simple mechanical valve. It would require temperature and pressure sensors for both the hot and cold water streams, and it would have to dynamically adjust the physical valve settings depending on all six parameters (position of the flow handle/slider/knob, position of the temperature handle/slider/knob, temperature of the hot water, temperature of the cold water, pressure of the hot water, pressure of the cold water). I'm not even sure this is possible with a fully mechanical system — likely some electronics would need to be involved, which might complicate things. --Waldir (talk) 10:50, 29 November 2022 (UTC)
Re: 'temperature of the hot water, temperature of the cold water, pressure of the hot water, pressure of the cold water' - those sensors already exist, inside the person using the faucet. If the water isn't hot enough, move the control in the hot direction. If the pressure isn't high enough, move that control in the direction that produces greater pressure. The (subjectively) prefect combination doesn't require the controls to be in the same position every time. -- (talk) 22:44, 29 November 2022 (please sign your comments with ~~~~)
"one for hot, one for cold, with the higher the slider goes, the more the flow is increased", you just described the standard two faucet system, :) Just, with round "sliders". :) NiceGuy1 (talk) 05:15, 3 December 2022 (UTC)

This is probably the very first xkcd comic where I have absolutely no idea where Randal is coming from. While different people have different preferences for different designs, I've never heard of anyone being confused by any faucet design. Maybe he's trolling us, by trying to get a rise out of people wondering what the hell he's talking about? Bischoff (talk) 08:20, 29 November 2022 (UTC)

Ummmm, being confused by unfamiliar shower controls is such a common shared experience that it has become a cliche! I'm sure there's an entry on TV Tropes for it, it's so common! (See Big Bang Theory, the very first episode, for an example. The movie Groundhog Day has an adjacent example that I think might not be there without this cliche). It seems weird to think there's anybody who hasn't had this experience, usually when showering in a hotel, or friend's house, or new house... Of course, 30+ years ago this wasn't a problem, everybody had the same two-faucet system, but more recently it seems like every shower has a different system. NiceGuy1 (talk) 05:15, 3 December 2022 (UTC)

This may be a reference to "Design of Everyday Things - Dan Norman" or books in that direction. Although he talked a lot more about creating doors wrong he also mentioned faucet designs as terrible. 09:17, 29 November 2022 (UTC)

I was initially drawn to the parallel/derivation from the "Build a better mousetrap..." concept, which vastly predates Don Norman. But it's such a widespread trope that I can't be sure it should be mentioned 'officially'. 11:13, 29 November 2022 (UTC)
I am actually puzzled by how many people don't relate to this, judging by the comments here. I guess I've been unlucky with the faucets I've encountered so far? Over the years I've had spontaneous conversations with multiple people abut how tap designs are either inconvenient (i.e. hard to find the right handle positions to produce the desired temperature and flow), or confusing to use, especially for hotel showers. In fact I'm adding this comment mostly so other people who share the same perception don't feel gaslighted or otherwise confused by so many people not recognizing this issue. --Waldir (talk) 10:50, 29 November 2022 (UTC)

Is that hairy? looks like him? Mushrooms (talk) 10:07, 29 November 2022 (UTC)

I think it could be, but he is looking different with the hair and because of the scruffy looks his hair standing up could be because he has torn in it. I think it is better not to include it as a Hairy comic. --Kynde (talk) 13:34, 29 November 2022 (UTC)

Is it too pedantic to point out the distinction between a helix (the shape of the control) and a spiral (mentioned by the character)? (talk) 10:28, 29 November 2022 (please sign your comments with ~~~~)

Not really, but it could be a very shallow (by radial increase/decrease per turn) 3D spiral, I'm more concerned by the "tightening", wondering if it's a flexible spiral/helix that is manipulated dynamically, rather than merely a tap* with a funny-shaped handle/head to rotate through into the backplate.
* - 'faucet' just makes me wait for a "force it" pun. It's a very American word that I'm not personally aware of being used throught the rest of the anglosphere. Maybe Canada, but probably not Aus/NZ/etc if my uptake of their TV/film exports is correctly remembered... Somebody may want to correct me on this issue, or add English As A Second Language metrics to this.
What is also interesting is that the 3D-perspective drawing by our in-frame inventor, upon the perspectivised drawing surface as depicted by Randall, makes it look like very much like an actual sticky-outy object within the drawn world. Like it's actually a moulded/similar relief model/mockup, surrounded by the more standard 'wall notes' used to suggest on-the-go calculations/annotations. An interesting artistic choice (or possibly an unintentional consequence) by Randall. 11:13, 29 November 2022 (UTC)

I think it should be added that the issue is mainly for the US. In Europe, and in the other of the rest of the world - except US - the thermostatic head has replaced most other faucet in shower, and the hand washing is not so much of an issue. My shower in some US hotels were a nightmare, where I remember taking multiple minute to understand how it might work. (talk) 11:03, 29 November 2022 (please sign your comments with ~~~~)

As a North American, I have to say I really don't know what you're describing. HOW do showers work? Controlling the temperature and water pressure??? NiceGuy1 (talk) 05:33, 3 December 2022 (UTC)

I think it should be added that the issue is mainly for Europe, especially Americans traveling in Europe. In the USA, where proportioning valves are common and anti-scald protection is mandated by code, controls are both intuitive and safe. (talk) 13:11, 29 November 2022 (please sign your comments with ~~~~)

So funny that these two comments in a row says the opposite. I'm from Denmark and where I sometimes dislike the designs of a faucet I have almost never found one for a tap that was a problem to understand. Sure for a shower there can be some issues, mainly because it can be too hot and problematic to stand under them when turning them on the first time. But it seems to me that this is not a serious problem in Europe. And from reading above it seems like this is in fact a US problem only. But the last comment says the opposite. by the way both sigantures unsigned, so did a check and found they where from two different IP and with time between. Was wondering if someone was trolling by writing the same comment twice with reversed meaning. But seems to not be the case. Have added signatures now. --Kynde (talk) 13:34, 29 November 2022 (UTC)
I vote that "confusing faucets" is an American problem. In some places it was hard to set the faucet exactly right (either because of faucet lag, which is the fault of the water lines and not the faucet anyway, or because the controls were highly non-linear around the target I wanted), but the direction in which the controls moved was always fairly clear.
I have been living in France most of my life, including visits to really old homes. I only ever met faucets of three kinds. In all of them water comes from a single outlet. Type 1 has two flow control knobs (one hot, one cold); type 2 has a single handle that can move in two angular directions (one for temperature, one for flow); type 3 (thermostatic valve) has one knob for temperature and one knob for flow. Faucets use types 1 and 2, showers can use type 1, 2 or 3. Only type 3 ever confused me the first time, and that was when I was a young child (I would guess age 8 or so?). I suppose the under-the-hood engineering gives rise to all sort of interesting tradeoffs between those three types, but from a user’s perspective they are all reasonable.
I have traveled to the UK multiple times and lived there for some time. It was mostly the same, though I have seen some dual-taps (essentially type 1 but with one tap per knob). It may be a bad user experience, but it is not confusing.
I have been to multiple other countries on short trips and do not remember any confusing faucets... except for one US hotel. That devilish shower had a single-knob control; the temperature increased over the whole range, and the flow was maximum at mid-range. I did not mind much that it does not explore the whole shower-space (the trajectory in the flow-temperature diagram was probably a super-optimized curve rather than a straight inverted V); but I did mind that it took a few minutes of exploration to understand what happened. 16:07, 29 November 2022 (UTC)
On the contrary, as a North American, I have primarily experienced this issue in North America. :) I mean, in 2020 I spent months in a hospital, each room I was moved to had different controls! (Luckily the last and longest was fairly similar to the second to last). And if you still think it's mostly an American-in-Europe phenomenon, just watch the very first episode of Big Bang Theory, where it's an American requesting assistance getting an American shower working. (Or, you know, this comic by an American about his American experiences).NiceGuy1 (talk) 05:33, 3 December 2022 (UTC)

My interpretation is that, for normal people, designing an intuitive faucet is easy: just one knob for temperature and another for flow. But designers seem to get overly creative for faucets and add all sorts of odd handles and gizmos. Figuring out a faucet at a hotel is often a task. Hence, in the comic, the designer is adding some sort of bizarre spiral handle when a regular one would be much easier. It's not that its hard to design a good faucet, but designers seem to have an odd blind spot for them. 13:48, 29 November 2022 (UTC)

VERY RELEVANT ASIDE Why aren't there digital faucets? And if this is such a bold idea It's mine 14:45, 29 November 2022 (UTC) paradoxical

There are digital faucets. Just google "IOT Shower faucet" or "IOT Faucet" I struggle to see any real utility to them however. --EvilGeniusSkis (talk) 17:15, 29 November 2022 (UTC)
I find analogue faucets to typically be really difficult to control. Turn knobs are fine, but lifting or turning a single handle like many faucets nowadays have just don't give me enough precision. Now, my hand-eye coordination and fine motor control are bad, but not entirely terrible. So I think for some people, even turn knobs are going to be annoying to use. So digital inputs would probably make it a lot easier if you have a motor disability. 20:55, 29 November 2022 (UTC)
My first thought is because they don't run any electricity lines anywhere near the shower when building bathrooms. Water and electricity is not a good mix. :) I've often seen showers which don't even have light fixtures above them in the ceiling! Bathroom plumbing uses physics alone, the only electricity is in another room with the hot water heater. NiceGuy1 (talk) 05:43, 3 December 2022 (UTC)

Damn, you mean people don't just switch on the tap and cope with cold showers? Damn, major L. 16:29, 29 November 2022 (UTC)

Just this morning, I was in the shower which has a single lever to control the mix of hot and cold water. I always turn it all the way up to get the hot water flowing and then move it down by small degrees until it is just right. With the lag in response for each successive change it takes a seemingly unnecessary amount of time to get it "just right". I would say that it is not so much "confusing" as it is "annoying". In this faucet there is no separate way to control the flow. The flow is maximized when there is an equal amount of hot and cold water, which of course is not necessarily the optimum temperature, because it takes a very small amount of cold water mixed with the hot to make it comfortable. Rtanenbaum (talk) 17:23, 29 November 2022 (UTC)

Regarding the transcript, which says "Below it is a box shape that dispenses water through a circle". What the ???. Can this be changed to, "Below it is a drawing of a spout"? Rtanenbaum (talk) 17:23, 29 November 2022 (UTC)

Well, its not really a box shape since its a 2D drawing and boxes are 3D... so it should say "Below are 3 parallelograms that form a two-dimensional projection of a rectangular prism..." Or maybe, for brevity we can just say "Below it is a drawing of a spout." 19:50, 29 November 2022 (UTC)
I completed the transcript but did not write that sentence. I have now changed to the short suggestion from you two :-) You are allowed to make such small obvious changes your self. Don't be shy :-D --Kynde (talk) 20:50, 29 November 2022 (UTC)

For hotel shower controls, even (especially?) if cleaned regularly, I find that they tend to lose the handy inlaid red and blue textures or overprinting to distiguish the relative functions of chrome or plastic dials and levers. But, even with them visible and discernable, they can be ambiguous. If a dial/rotary component has hot/cold (or flow-control) markings on the fitting it is sat upon then it tends to show which direction to twist it for which change. But if it's marked on the dial then there's two opposing conventions used for a fairly standard "arrow with increasing line-width towards the head" marker:

1) Twist the dial in the direction of the more blue bit (incidentally showing more of the opposing red arrow) when you want the cooler temperature, this being a 'turn this way for more "blue water"' sort of thing,
2) The thicker bit of blue is supposed to be read as aligned to something subtle, like a notch/ridge mark, upon the static backplate, meaning that you should twist the dial in the opposite direction to bring the "more blue" into play.

...though some (like central-heating radiator controls) do disambuguate this by having the red/blue meshed long thin triangles (and maybe digits/tick-lines to easily establish a position and any small change) hidden within a shroud with just a small window upon the 'meaningful' uppermost/foremost bit of the twisting pattern. Of course, the chances that any one hotel's chosen fitting is easily recognisable as the same as the last one you used in a different hotel (or the last visit to this one!) are not great. I'm sure there's going to be someone who collects "hotel plumbing" photos, or similar, to catalogue their sheer variety. Certainly it's something I might have wished to have started to do, but seems a bit late to begin now. 19:37, 29 November 2022 (UTC)

Here's an idea: put a little plastic window on the faucet and have the colour behind it turn red or blue. So depending on how it's made, the blue/red thing turns behind the plastic window, or the window shifts over the blue/red thing. Either way, if you can only see red, it's hot; and if you can only see blue, it's cold. And the colours won't get worn away since they are behind a little window. 21:02, 29 November 2022 (UTC)

You know, it seems like the most common complaint with faucets of any kind is that the sweet spot between hot and cold is so hard to hit. Meanwhile, most of the range is used for various degrees of cold water which barely feel different. It reminds me of linear rgb, where most of the range is used by bright looking shades, with it only getting darker rapidly near the black end. I think a good start for a better faucet would be nonlinear mixing, where the knob gets less "sensitive" as you move it towards hot. This would sacrifice precision for cold temperatures, but how often do you really need a specific cold temperature (aside from fully unheated)? 08:44, 30 November 2022 (UTC)

Delta makes a tub control/spigot that flummoxes every visitor to my home: The control is single-action [temp] but to turn on the shower you have to pull down a ring under the tip of the spigot. I give a ‘lesson’ to every new visitor now. 12:03, 30 November 2022 (UTC)

Uh, in all the two-faucet systems I've ever seen in my life, I have NEVER seen or heard of the hot and cold having uneven water pressure or one overpowering the other or the cold premixing into the hot or whatever complications are being invented in the description, ???? Sure, the don't flush the toilet, don't run the washer/dishwasher thing, that's super common and widespread, but that's nothing to do with the two faucet system, that's just the physics of water. And my experiences are VARIED, from up-to-date houses and nicely maintained hotels all the way down to "This cabin barely has indoor plumbing". NiceGuy1 (talk) 05:51, 3 December 2022 (UTC)

Here is a system to add to the list. Three taps. Separate Hot and Cold bath taps plus single (one-degree of adjustment, first on/more water then more hot) for the shower. Only took a moment ir two to work it out (without glasses, I hadn't read the notice). 17:31, 3 December 2022 (UTC) - PS, as I don't have any mainstream social media presence, I was wondering if Kiri at Staverton Park can be mentioned here? The room was as neat and tidy as I might hope to expect, and I wouldn't want to penalise her just because of my failings...

Is this just a Maryland thing?: Every private home I've lived in since moving there has the same horrible one knob / one movement control. Off is the far clockwise position. As you rotate the knob counter-clockwise, both the water pressure and the temperature rise in concert. As a result, the water blasts out of the shower head at full volume at any comfortable setting. (Signing an old comment) These Are Not The Comments You Are Looking For (talk) 14:52, 3 November 2023 (UTC)

If you don't want confusing faucet controls, make Hot/Cold two sliders, then put meters on each so you could see the cold% and hot%. Simple. Psychoticpotato (talk) 18:06, 3 May 2024 (UTC)