Compatibility constraints of the water cooler

Raymond Chen

One of the things you learn when dealing with compatibility is thatevery single external detail is a potential compatibility constraint.

A few years ago, the water coolers in the buildings were replaced.I have no idea why.Maybe the new water cooler company put in a lower bid.Who knows?All I know is that I like the newer ones less,and I’m not the only one.

The water cooler has three spouts:one for hot water,one for room-temperature water,and one for cold water.(Okay, so it’s also a water heater as well as a water cooler.)The old machine positioned the spouts close enough together thatyou could fit a cup beneath the last two spouts(room-temperature and cold).This meant that you could push both levers to dispense waterinto your cup.Now, the result was “somewhat cool” water, but the important thingwas that it filled your cup in half the time!

Hot Temp Cold
  |   |   |
  v   v   v
     |.   .|

The new water coolers has the same three spouts,but they are positioned just a tiny bit further apart,just far apart enough that you can’t use the “double-barrel” trickany more.

Hot  Temp  Cold
  |    |    |
  v    v    v
      |.    |.
      |.cup |.dribble

The new water cooler is subtly incompatible with the old one,in a manner that is not part of the specificationbut rather is merelya convenient side-effect of the implementation.