Electric showers are very common in the UK - although the heater is in a wall-mounted unit, with the head on a hose, rather than the heater being in the head itself.

The heating element has three layers - innermost, a wire that gets hot. Around that, a ceramic insulator. And outermost, a metal cover to protect the ceramic insulator. Then the heating element is mounted in a small water tank. And that, along with some other components, is put into a suitably waterproof outer plastic box. The insulation is of course all tested at the factory.

The tank, heating element outer, and all the pipework in the general vicinity is then grounded, and the power supply passes through an RCD (our equivalent to a GFCI). There are also two or three temperature sensors, and a water pressure sensor.

Installers also have to have an up-to-date electrical safety license - so for they know better than to (for example) compromise the waterproofing of the enclosure by adding extra holes to make the wiring simpler.

In some countries, electric showers use a metal coil as a heating element, similar to a spring, located directly in the showerhead. When you turn on the faucet, water fills the showerhead and touches the metal, effectively bringing the positive and negative wires into contact. The coil then heats the water as it flows out. Occasionally, the coil can oxidize or break if there's not enough water running to keep it cool. When that happens, most people replace it themselves.

A lot of things involving electricity in places with type-G plugs seem more dangerous if you don't know/assume that almost everything is grounded. Took me a while to realize that hairdrier he mentioned in the blogpost likely didn't have a ground connection in the plug.

In the case of a toaster with a grounded frame, the most likely route for a short is straight to earth which will trip the RCD on that set of plugs.

Toasters (usually?) don't have RCD (what they call GFCI in the UK) in the US. Maybe your circuit will have a GFCI, but it depends where you put your toaster. Do all circuits have RCD in the UK?

Most buildings that were built or have had substantial renovation work done will have RCDs installed, yes.

While you can have a separate RCD for each circuit, and the newest installations do, it's more common to have two RCDs in the panel/fuse box/consumer unit, with each circuit on one or the other. This arrangement is known as a 'split load consumer unit'. The intention of having two instead of one is that plugging in faulty electronics at night not plunge the entire house into darkness. These RCDs usually have a trip current of 30mA, making them less sensitive than American GFCIs which trip around 5mA.

i'm pretty sure that the electric showers i've used didn't have the sealed magnesia insulating layer you're describing, nor were they connected to an rcd/gfci

i do agree that the measures you're describing would make them much safer

Your local codes almost certainly say no electrical outlets in that zone, not no electricity. The assumption being hardwired devices installed by professionals are not a huge risk.

There's a reason you don't see this type of water heater in most of the world.

I wonder, though, why there are so few incidents where this type of shower is prevalent, given that people not used to it are so worried. If the fatality rate were 0.0001%, hundreds of people would die every day.

Just in this thread alone we've found several stories of people being mildly shocked by these devices while on vacation.

It's not that people die every day from these devices, it's that in general this isn't a great way to heat water if you have alternatives available.

I don't know about you, but I would prefer not to receive a shock, no matter how minor it might be, when I step into the shower...

yes, and that reason is mostly the kind of people who were asking the original poster how he made it to adulthood

Right, I'm sure it has nothing to do with the plethora of "shocking" tales regarding these water heaters.

I can count on zero hands the number of times my shower has given me a jolt, even a minor one.

We mostly see these types of devices in relatively poor countries without the means to install more modern and safer alternatives, such as whole house water heaters.

You're absolutely right that they're common in poor countries and that we can't afford more modern and safer alternatives. Not to mention that the more modern alternatives heat the water much more effectively, providing way more comfort.

no, electric showers heat the water much more effectively, providing way more comfort; here in argentina i have to wait 45 seconds or so for the shower to stop running cold because the hot water has to run all the way from the hot-water tank in the kitchen. and i have to cut the shower short after about 20 minutes because i run out of hot water. i had the same two problems when i lived in the usa, though constant-recirculation systems have become more common there in recent years, solving one of them

electric showerheads, by contrast, provide instant heat, and they provide it for as long as you care to shower. what they don't provide is hot water in the sink for washing dishes, unless you take the dishpan to the shower to fill it. and if they're incorrectly installed they can be deadly, but that's a pretty rare problem both with hot-water tanks and with electric showers. i've never talked to anybody who knew anyone killed by an electric shower, and the nature of electrocution is that it's unlikely to injure you without killing you

(tankless hot-water heaters, called calefones, are common here in argentina, and they also solve one of those two problems—the other one. rooftop evacuated-tube hot-water thermosiphon hot-water heaters are also somewhat popular here)

i think that, aside from dishwashing, the main advantage hot-water tanks have over electric showers is that historically natural gas has been much cheaper than electricity. since chinese solar panel producers have driven the cost of solar panels down by a factor of 20, that's not necessarily true anymore—but the intermittency of solar-energy production favors hot-water tanks, if anything, even more strongly

apparently electric showers are common in the uk, which is not a poor country: https://news.ycombinator.com/item?id=41250251 but with much better safety measures than i'm used to seeing in latin american countries

You're right that electric showerheads provide instant heat. My comparison was based on the electric showerhead I have at home, which can't heat very much due to electrical limitations. It's definitely not the case of every installation. On the other hand, the hot water I experience when showering at the gym or in fancy hotels is extremely, extremely hot and much more comfortable on a cold day. I also see some wealthy people installing gas heaters in their homes, which is why I associated electric showerheads with a lack of options.

oh, yeah, i don't think an electric showerhead in my house would work very well at all; some dumbfuck wired it with 15-gauge wire (1.4mm diameter, safe for up to about 10 amps) and at 240 volts you need more like 40 amps to provide a comfortable shower, depending on water flow rate

the entire house is on a single anemic 25-amp circuit breaker. at a low-flow 6 liters per minute (100g/s) heating from 15° to 40° (Δ temp = 25 kelvin) at 4.2 joules/°/gram, you need 10.5 kilowatts, which is 44 amps at 240 volts. at 120 volts just forget about it

i have had a super cheap non-tankless electric shower in a couple of places i've lived in argentina, which sucked. you would fill it up with water, plug it in to start heating the water, unplug it half an hour later to stop heating the water (hopefully before it overheated), and then open the valve at the bottom to run the shower. dangerous, inconvenient, and uncomfortable

on the other hand, if you're building an apartment building in brazil or a hotel in costa rica, there's nothing stopping you from including an 80-amp circuit in every bathroom for the electric shower. it's definitely cheaper than a hot-water tank or a tankless heater, and it might be safer too, since it might allow you to avoid running gas to the room

>on the other hand, if you're building an apartment building in brazil or a hotel in costa rica, there's nothing stopping you from including an 80-amp circuit in every bathroom for the electric shower.

Do these countries not have any limit on the current in a circuit? Over here we're not allowed more than 16A in residential use and that's over 2.5 mm^2 wires. What kind of conductors do they use in Brasil for 80A circuits?

i'm not familiar with brazilian regulations but normally 80 amps would be about 3-gauge, 26mm². you can bend it with your bare hands if you get the stranded stuff. here in argentina people are evidently a lot more lax than that, so maybe in brazil they are too, but clearly you need at least 12mm²

I had one of these in an outside room as a teenager and in the winter it was terrible:

You can only heat water so much for the available wattage and when it was cold the water was so cold that only a thin trickle could be heated to a comfortable showering temperature.

i admit i've only used them in countries that don't really have winter, where they were great. except the time i got shocked

no?

i mean it's the same reason most people in the usa don't have a bidet in their house; it's not because they're too poor to afford one. technology adoption is path-dependent and mostly random, and fear makes people conservative. yes, there are a few people who are familiar with the actual risks and rewards of the different technologies, but they're vastly outnumbered by the pre-galilean minds who are entirely guided by conventional wisdom

most people in the usa can count on zero hands the number of times they've sprayed water on the bathroom ceiling from their bidet, too

This assumes a bidet is objectively better than a regular toilet. That is debatable.

It's not debatable these electric showerheads are objectively better, just because some poorer communities around the world use them.

well, it only assumes that bidets are subjectively better to many people, which they certainly are; it doesn't rely on the assumption of an objective, observer-independent scale of valuation in the way you're describing

(bidets aren't an alternative to a regular toilet, and the fact that you think they are is a minor indicator of why it's difficult for even widespread, highly beneficial innovations to become universal even after centuries)

not only is it debatable whether or not electric showers are better in that sense, i have in fact debated it; i refer you to https://news.ycombinator.com/item?id=41250642 and eagerly await your opinion

If given the option, free of charge, to continue using electrified showerheads or using whole-home water heating... how many would continue to use electrified showerheads?

The fact that they are only common in poor and impoverished areas, tells you everything you need to know.

This argument is a lot like asserting instant-coffee is better than fresh brewed coffee because some people have no alternative choice.

probably most people would continue to use either what they're familiar with or what they think is fancier, with little regard to what they would actually like more—in the same way that many people have opted to live in suburbs where the commute makes them miserable, or drink and smoke heavily despite the impact on their health, or date abusive partners

humans are not automatically strategic. one reason is that they're subject to many kinds of irrationality; the particular species you are currently exhibiting is known as 'the fallacy of affirming the consequent'

a pretty large fraction would continue using electric showers just because they're familiar with them—but that is at best only a very weak argument. we can do better than that by debating their actual advantages and disadvantages, as i did in the linked comment, rather than mindlessly subscribing to vox populi, vox dei

if given the option, free of charge, to install a bidet in your house, would you take it? evidently not, because you don't know what a bidet is or how to use it. the same could be said of most people installing a computer in their house 50 years ago. or many modern innovations today, like a gfci, corningware, and borosilicate oven dishes, some of which have fallen out of use because consumers didn't understand them

using a cellphone instead of a landline was only common in impoverished areas 30 years ago, and even today, having front-door locks that are hard to pick are still only common in impoverished areas. also, speaking lingala is only common in impoverished areas. that's not because there's anything wrong with lingala

finally, as it happens, my wife prefers instant coffee to fresh-brewed coffee

This is a dangerous myth. Electricity takes all available paths, with less current flowing through the paths with greater resistance.

As far as I understand, the main reason people don’t get electrocuted even with improperly grounded shower head heaters is that (as noted in the post), tap water is generally not very conductive in the first place, so you’ve effectively got a gigantic resistor between you and the wires (assuming there’s a continuous path through the water at all). So even if the least resistance path is through you, the amount of current will be tiny due to Ohm’s law.

It's not a myth. Your second paragraph basically agrees with me and contradicts itself.

so you’ve effectively got a gigantic resistor between you and the wires (assuming there’s a continuous path through the water at all). So even if the least resistance path is through you, the amount of current will be tiny due to Ohm’s law.

That is, by definition, NOT the "least resistance path".

> It's not a myth.

Yes it is. A tip: if someone tells you something is a myth, your next step should be to google it. This is intro level parallel circuit stuff.

Hell, just think about the circuitry in your house. If you have your phone charging on one outlet, and you plug a hair dryer into the adjacent outlet, does the phone stop charging? Does the hair dryer not run? Do you think those things have exactly equal resistance? Of course not. Current flows to both of them, but more current flows to the hair dryer.

> That is, by definition, NOT the "least resistance path".

I don’t think you know what “by definition” means. You could be the only path for the electricity to flow, and if there’s high enough resistance, it won’t hurt you.

Please stop repeating this nonsensical folk wisdom. It can get people killed.