This is probably a dumb question but why do we add cold water to the reservoir? Why not hot water to speed thing up? This seems to be a reoccurring theme with all things from rice cookers to espresso machines.

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It seems, at least with us here, that hot water out of the boiler (or tap) can contain more metals. On the other hand one would think hot water in the tank is good for temperature stability. And of course your HX flush would have to be looooong!

I would also think that cold water would be used for the same reason as for making tea, better oxygen content and (possibly) fresher taste.

I'm surprised that there is not more discussion of reservoir water temps, given that so much attention is paid to brewing temps.

The incoming water in my Gaggia can vary from very cold (just refilled in the morning) to very warm (machine has been on for 1+ hour). With such a small boiler, I know that this affects my intrashot brewing temps.

But can't the same be said for HX machines, i.e. flush amounts, etc.? Or plumbed machines in winter vs. plumbed machines in summer?

Not rocket science... I'm just surprised that this parameter is usually overlooked in temp surf discussions.

nixter wrote:This is probably a dumb question but why do we add cold water to the reservoir? Why not hot water to speed thing up?

In addition to the reasons already mentioned, another good one is that Ulka vibratory pumps are not rated for pumping water at temperatures above 25C.

portamento wrote:But can't the same be said for HX machines, i.e. flush amounts, etc.? Or plumbed machines in winter vs. plumbed machines in summer?

Ideally the water tank temperature isn't dramatically different than room temperature - or at least stable (I have measured temperatures of +90F after hours of idling). FWIW, I have an empty filter canister for my plumbed in HX espresso machine to buffer differences in incoming water temperature.

The usual advice is never to use hot tap water for drink or food; most home hot water systems leech too much metal to make using it a safe long term practice. Instant hots and Japanese style hot water dispensers are the way to go for quick hot water.

As Dan says, the actual temperature of the water in the tank is irrelevant. In HX machines, maintaining a consistent tank or inlet water temperature is an issue, since the HX heats the water from that starting point. Single or double boilers machines heat the water to a fixed temperature, so the tank is not an issue.

If I were to be utterly anal, I'd not just start my machine well ahead of first use, I'd also refill it with a little water after each use to maintain the same water level and the same equilibrium temperature (the less water in the tank, the warmer the equilibrium temperature). However, I never noticed an actual difference between late in the day, low tank shots, and early in the day full tank ones. So I'm passing on this.