Concerning Baths and Showers

A recent trip by car most of the way across the country and back provided me a substantial sample of motel showers. The most recent, in a Hampton Inn, was a good example of bad design. The shower stall was rectangular and fairly large with the control located under the shower head. Turning it on subjected me to an initial cold shower — followed,  if I turned the control too far in the process of adjusting it, by a burning hot one.  Since the same control both turned the shower on and set the temperature I did not have the option of setting it to my guess at the right temperature first.

A motel earlier in the trip had a similar shower stall but sensibly located the control at the end away from the shower head; I could turn it on and adjust to my desired temperature before getting under the shower. A simpler solution, common in older and less fancy motels, is a bathtub plus shower. You turn on the water and adjust the temperature before switching it from tub to shower. A further advantage of that design is the option of taking a bath instead of a shower — or disadvantage if a member of your party is in the habit of tying up the bathroom for hour plus hot baths.

So much for American  showers. European hotels usually have two shower features uncommon on this side of the Atlantic, at least in the motels I stay in — a hand held sprayer in addition to the fixed shower head and a shower head with adjustable height. Point the sprayer away from your body, turn on the water and adjust the temperature to what you want. Some have additional bells and whistles.

All of the showers I have encountered, American and European, share one major defect: You adjust the temperature to what you think you want, get under the shower, discover it is too hot, make a small adjustment of the control and it is now too cold. Since the full range of the control is from all cold water to all hot water even a small adjustment produces a substantial change in temperature.

One solution, borrowed from the standard design of microscopes, would be a coarse control plus a fine control; you use the coarse to get the temperature to something close to what you want then switch to the fine to adjust about that temperature; it’s an obvious solution but one I have never seen. A more elegant solution would be a non-linear mapping from control to temperature. Suppose the control can be rotated through an arc of two hundred degrees. The zero degree position is pure cold, since there may be some masochists who like a cold shower to wake themselves up in the morning. The two hundred degree position is pure hot, since the water heater might be malfunctioning and producing only lukewarm water. But the first twenty degrees of rotation map into the range from 0 hot water to .6 hot water. The final twenty degrees map into the range from .8 to pure hot. The other hundred and sixty degrees cover the range from .6 to .8, giving me much better control over the temperature in the range I care about.

An improved model could have an adjustment to shift the location of the central range, used once and then left alone. For the Silicon Valley market we could have an intelligent version which keeps track of what temperature the user prefers and adjusts its central range accordingly. The next year’s model could allow for up to four users with different tastes in shower temperature. Step into the shower, tell it who you are, and it automatically chooses a mapping that makes it easy to control the temperature over the range you care about.

A different improvement would be a thermostatic shower, one which maps the setting of the control not to the amount of hot and cold in the mix but to its temperature. Turn it on and for the first few seconds nothing comes out because the hot water isn't, having cooled in the pipe between the water heater and the shower. When the temperature of the hot water reaches the level set on the controller the shower turns on as pure hot, adjusts the mix thereafter to give the temperature it is set for.

Which of these already exist? I have encountered none but have been told that thermostatic showers, at least, exist.

Showers, Tradeoffs, and Gift Horses

I interpret a shower with the control under the shower head as simply bad design but that may be a mistake. Having the controls at the opposite end of the enclosure from the shower head lets me adjust the temperature of the water before subjecting myself to it. But the farther the control is from the shower head the longer it takes for the changed mix of hot and cold water to get from the control to the shower head, hence the slower the process of adjustment.

This is one example of a general point. Consider any system—a shower, a car, the human body—that has been optimized, whether by human design or evolution. If changing the system in some way, in my example moving the control farther from the shower head, produces a benefit, it must also produce a cost, since otherwise the change would already have been made in the process of optimizing the system.

Always look a gift horse in the mouth.

Concerning Bathtubs

Showers do not have a coarse/fine control system but humans do. When you first encounter water it is, unless you are very lucky, either too hot or too cold. Once you have been in it for a while your temperature sensing system adjusts, becomes sensitive to small changes around the current temperature.

This feature of the human sensory system is responsible for one of the problems with bathtubs: Water warm enough to be comfortable for a long soak is hot enough to be painful at first encounter, water cool enough to be comfortable to get into is insufficiently warm for the long term. The solution is a bathtub with an adjustable thermostat. Set it initially to the “comfortable to get into” temperature. Get in, press a button, and it warms to your long-term optimum. It could be done with off the shelf technology — we already have thermostatic heaters for fish tanks. Also hot tubs.

The cruder equivalent is to be your own thermostat. Start with water not quite too hot to get into, warm it to the temperature you want once you are used to it by letting out warm water, putting in hot, repeating as necessary to keep it comfortable. It is less energy efficient than the higher tech version but better than being scorched at the beginning, chilled thereafter.

A practical problem with this comes from the construction of bathtubs. Typically the controls, drain, and faucet are at one end. Since you would prefer not to experience the additional hot water directly against your skin you locate yourself at the other end — only to discover that the controls for letting cool water out or hot in are now out of reach.

Which is why bathtubs should have faucet and drain at one end, controls at the side — you don’t want to lean against them — near the other end.

Wanted: A Computer for the Bath

A long bath requires entertainment. That used to be a paperback that I was willing to risk getting wet but nowadays my entertainment is online, arguing with people, browsing the web, playing computer games. I could put a board across my (large) bathtub and put my laptop on it but dropping my laptop into the bath would be a more serious matter than dropping a paperback in. With enough ingenuity I could probably kludge up a more practical setup, perhaps a computer and large screen somewhere else in the room and a wireless keyboard and mouse, or mouse equivalent, preferably waterproof. But I suspect that doing so would be expensive in both time and money.

Surely I am not alone in my preferences. Surely there is a market niche here waiting to be filled.

P.S. A commenter on this post describes his bath in Japan, which seems to be everything I could want, aside from the computer. Other commenters report that waterproof kindles or a kindle or tablet in a waterproof case provide a solution to that problem — but neither a kindle nor a tablet is a full substitute for a laptop or desktop.