Much of the confusion in this thread comes down to the fact that in the US, the standard shower valve is a 'pressure-balanced' valve, which allows you to select a flow-ratio between hot and cold feeds, but does not in itself maintain any particular temperature - it just ensures that in the event of pressure changes on one or other feed, the overall mix is maintained (preventing temperature spikes if someone flushes a toilet).
Whereas in many other parts of the world, the standard shower valve is a 'thermostatic mixing valve', which allows you to select a temperature, and balances the inputs to achieve that desired temperature mark.
Note that if you go to, say, HomeDepot.com, and look at shower faucets, you will not find thermostatic mixing valves. Only pressure balanced. The only thermostatic component in conventional american shower valves is an anti-scald-cutoff. Thermostatic valves do exist, but they're not the ones that are bundled into showers and that therefore get employed by the average landlord who is grabbing the cheap standard parts off the shelf. Thermostatic is a premium option, and not one that even crops up in the search result filters for showers.
So most Americans have simply no idea that thermostatic valves are a thing.
Whereas if you go to, say, diy.com (which is the store of B&Q, an equivalent store in the UK), and look up showers, you will find all the basic 'mixer showers' have thermostatic valves.
There's something on-brand about a software engineer seeing a problem, and spending a great deal of time fleshing out his solution to the problem, even asking manufacturers to reach out to him, yet missing the easily-findable fact that thermostatic valves are a thing. At the end he concedes that someone else must have already tried his idea but doesn't quite get to the idea that someone else probably found an even better solution.
Well, people may not know what they are and many are certainly expensive (>$80), but there are a lot of them at your local home center. Some are just "Heat Guard" (160/135F), but most of them are full mixers with the little expanding wax valves.
As an aside, I just want any form of mixing tap for my sink in the UK, but apparently that’s still too much to ask for in many buildings here so I’m left with the separate hot/cold taps that are inevitably too far away to sort of “splash together.”
In codes written before GFCI, making sure you can't electrocute yourself by accident could be achieved by:
a) establishing a minimum distance between the sources of water and electrical switches that would have to be measured, inspected carefully, be expensive to re-do, and possibly not be practical inside a small bathroom, or
Here's a scenario: you took a nice long hot bath. It got dark outside. You get out and want to turn on the light. Do you want to open the door and let the cold air in? Do you need to cover yourself first?
Crack the door open, reach through and flip the switch. It's only going to be momentarily cold and if covering is required a quick wrap of the towel will suffice.
I've been in a multi-stall public bathroom where a person leaving turned off all the lights. For private bathrooms, I would much prefer to have the light control fully within my control while I am inside the bathroom.
> So most Americans have simply no idea that thermostatic valves are a thing.
Having very limited travel experience outside the US, my mental model of what the temperature control on showers was supposed to be doing was thermostatic, and I just assumed that they were just bad at it. You may have just explained one of my longest running minor peeves, which is that I've always found it basically impossible to maintain a shower temperature I find comfortable without needing to make adjustments. Given that I don't own my home at this time, I probably can't do anything about it any time soon, but at least from now on when I have to deal with the fluctuations in temperature I'll know that I'm not crazy and this is actually expected behavior.
It gets even worse when the water heating is flow activated (switching between 0 and 100%) and your faucet/shower head is too gunked up to allow for enough flow from at the desired hot/cold mix.
Yes, our thermostatic valve has around 270 degrees of travel on the temperature dial (which is separate from the water flow dial). Of those 270 degrees, it takes about 140 degrees to go from my preferred temperature to my wife's preferred temperature. With that large a range I can just turn it to roughly the right place before turning the water on and it's always just the right temperature. This isn't the cheapest valve (about £190) but I think many cheaper thermostatic valves are probably just as good.
I don't think you need temperature sensing to achieve what the author wants: you just need the amount of hot water mixed in to follow a specific non-linear curve. We just want to adjust sensitivity on an already-functional mechanism.
Given my understanding that water heaters are all calibrated for approximately 140°F, then even assuming some fudge factor it seems possible to do better with pressure-balanced valves than we have today. Especially if the valve could be calibrated at install time.
I think a lot of the US fixtures don't even have compatible thermostatic valves. You'd have to get a complete replacement fixture, not just a valve/cartridge/insert.
You could define the desired characteristics in the shape of a curved hole within ceramic disks, such as the type commonly used shower faucets currently.
Whereas in many other parts of the world, the standard shower valve is a 'thermostatic mixing valve', which allows you to select a temperature, and balances the inputs to achieve that desired temperature mark.
Note that if you go to, say, HomeDepot.com, and look at shower faucets, you will not find thermostatic mixing valves. Only pressure balanced. The only thermostatic component in conventional american shower valves is an anti-scald-cutoff. Thermostatic valves do exist, but they're not the ones that are bundled into showers and that therefore get employed by the average landlord who is grabbing the cheap standard parts off the shelf. Thermostatic is a premium option, and not one that even crops up in the search result filters for showers.
So most Americans have simply no idea that thermostatic valves are a thing.
Whereas if you go to, say, diy.com (which is the store of B&Q, an equivalent store in the UK), and look up showers, you will find all the basic 'mixer showers' have thermostatic valves.