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Comment by PaulHoule | Hacker News Reader

I think the current ones are the way they are because the input temperature is not well controlled. I live in an old farmhouse where the cold water gets really cold in the winter and for years we've had a tankless water heater that has never worked that well but lately has gotten full of scales. We haven't tried descaling it because we're concerned that we'll kill it in the process of descaling it and won't try it unless we have a replacement lined up.

All of that means that the input temperatures are poorly controlled even when the heater is working.

The very large range of mixing ratios helps compensate for uncontrolled input temperatures. If the input temperature was better controlled (say with a thermostatic function) you might be able to calibrate the valves to a user-appropriate range, but barring that you'd need to put a thermostat right after the valve.

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It's obviously your risk not mine, but I wouldn't be particularly concerned with descaling a tankless with vinegar causing a problem. I'd be more concerned with the uneven heat transfer causing damage (by overheating the metal that doesn't have adequate cooling from the water [that you're intending to heat]) than I would from the descaling causing damage (or more precisely, revealing existing damage).

You're supposed to descale them every year anyway

Another problem is the difference of pressure between the cold and hot water tubes. It's usually not to much, but I remember than in one hotel the difference was so big that if I opened both taps normally, I only got cold water. Moreover, the cold water entered into the hot water tube, so after closing the cold water tap I got only cold water coming from the faucet for a while. The solution was to open the hot water tap completely, and make a tiny turn in the cold water tap.

Or to put it another way: Spolsky said that users don't use 90% of the features in any app; unfortunately, they each don't use a different 90%. You don't use 90% of the shower faucet ratio range; unfortunately, each house doesn't use a different 90% of the ratio range...

Thing is, that 90% of the range is going to mean that you and I pick a different range from "hottest" to "coldest", right?

So it wouldn't be beyond the wit of man to fit a couple of setscrews, possibly accessible by popping the knob off, to set the "low" and "high" stops for the thermostat in the shower valve, right?

You'd think, eh...?

GNOME argument strikes again.

I don't use the acceleration and brake on my car all the time. I use the doors to enter or leave the car. I use the electric windows when i insert the parking ticket.

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