Hi:

My five-year-old Isomac Tea is getting tired, and I think it's earned its retirement. (My La Cimbali, Jr. grinder is in its prime and seems to have a long career ahead of it.) I'm trying to decide between a PID'd Quickmill Alexia and a first-class HX machine, though I haven't ruled out a good double boiler, PID'd or not. I drink straight espresso almost exclusively, maybe two cortados a month. Like me, the people I entertain drink espresso almost exclusively. I rarely need to make more than one milk drink per hour. I typically pull two doubles every morning, and three to six doubles in the evening when I entertain once or twice a month. I rarely use the machine in the afternoon.

I understand that HX's have an advantage over double boilers in that an HX will never have water remaining stagnant in a metal boiler. Do HX's have the same advantage over single boilers? If so how significant is this parameter compared to the question of temperature stability? I'm not inclined to delve too deeply into techniques of HX temperature control, which is why this is an issue for me. (I know how to execute a basic cooling flush, which the Tea pulls off in about 25 seconds, but that's about it.)

I know there are other issues but I think I know how to think about them. This one has me stumped, and I have failed to find an answer by searching this forum. That may be because I din't use the right search terms, and I apologize if this is a repeat question. Can anyone help me? This is a very helpful site.



Thanks,

Jacob C.

Hi, Jacob -

In terms of temperature stability, I don't think that stale vs fresh water is an issue. A single boiler with a PID is going to require less effort and attention to get consistent brew temperatures compared to an HX. OTOH, the HX gives a better opportunity to change brew temp "on the fly" by changing your flushing routine.

I also am a straight shot drinker, and have gone the PID single boiler route. I have not noticed any taste defects associated with stale water in the boiler. But I also have no basis for comparison since I've never owned an HX machine.

I worry more (but still not very much) about the effects of warm water sitting in the plastic reservoir than I do about water sitting in the boiler. And if you buy a pourover HX, you'll still have the reservoir water "problem."

Jim

This topic was discussed in Can water go stale? and Tasted Your Reservoir Water Lately? where I suggested a simple test to determine if a boiler imparts a taste:

• Flush down the boiler completely and refill it
• Wait until the boiler stabilizes at brew temperature, and then draw a sample
• Leave the machine idle for 24 hours and draw another sample
• Taste the two samples at the same temperature (room temperature or heated to say 150F).

Mark reported these results for his Expobar Brewtus, which has one of the largest brew boilers around:

Dogshot wrote:The only lesson I took from this was that the most important element to achieving the best water as a base for the coffee is to completely exchange the water in the reservoir every day. This would be true for any machine that runs off a reservoir.

I haven't tried the above experiment with them, but I believe water idling in smaller single boilers like the Rancilio Silvia and Quickmill Alexia shouldn't be an issue since they are flushed enough through normal use that the water doesn't sit long enough to pick up a metallic taste.

To round out the discussion, I noted the Ponte Vecchio Lusso's combination steam/brew boiler imparted a metallic taste to the water after a day or two. You may not taste it over the strong espresso flavors, but I would flush its boiler regularly on principle alone.

Thanks for the helpful replies. I'm not surprised this was discussed before, and that I just didn't find it. Ironically, the analyses have made me more open to a double boiler, as there seems to be ways to minimize the fresh water problem. Thanks again.

Jacob C.