I just started making espresso from my first respectable machine (2011 Lelit Anna PL41 EM), which I completely disassembled as part of my refurb, and it occurred to me that, in all the material I've watched, or read, nobody seems to purge the water sitting in the machine between shots.

Because I had the machine completely apart, and completely dry, when I reassembled it I had the opportunity, and thought to do it, for measuring the amount of water it takes to fill the system; a little over 250 ml, as it turns out. Since I only pull one, or two shots a day, should I purge that water before pulling a shot? Should we all purge that water before the first shot of the day? How long can we let that water sit in those copper, PTFE, silicon tubes, and a big, brass boiler before we think it should be cycled through?

Assuming that the three-way valve is working properly, I personally wouldn't worry about it much past "routine cleanliness".

Water sits in your municipal water piping for "ages", though it is protected with chlorine or chloramine. Beverage people often pull these out, or are mixing from bottled or distilled water. Without the disinfectant, it is possible for "stuff" to grow, especially in the warmth of the water reservoir.

For my risk tolerance, clearly stating that everyone needs to make their own decisions, I clean my reservoir with soap and water weekly. With an E61 groups that shares its exhaust path with the brew path, I'd use a cleaner like Cafiza somewhere between weekly and monthly. The back flush was mainly for taste, but probably helped keep any unexpected biologics at bay.

I use water bottled by the gallon that my machine's manufacturer directly recommends. Any interesting test would be to pull an empty basket shot or no portafilter into a cup. Then let it cool and taste. I may have to try that tomorrow....

I might but rarely purge other than for reasons relating to temperature but not water quality & safety. Copper has some of its own inherent disinfectant properties as well as the brew boiler temperature is high enough to kill most things almost on contact at espresso water brew temperatures.

I will do some purging after returning home from a vacation where all the direct plumbed water inlet ¼-turn ball valves have been closed OFF for some time. That might be done with water cold, hot or both.

GDM528 wrote: OMG - genius! I just tried this: both taste the same, whew!

I'm afraid to try it! If it doesn't taste identical then I'll be down a rabbit hole for at least a week trying to figure it out

I think the OP may be concerned about possible lead migration from the boiler (the brass base is supposed to be plated but could wear through) and is wondering if purging water that has been standing in the machine might lower the risk of lead exposure, based on the assumption that more lead would be released into water the longer it stayed in the boiler. Am I correct, CareyB?

If that's your concern, I don't know the answer, but suppose it might make a small difference.

Interesting. Perhaps a quick water lead test would alleviate (or make for great panic) that concern?

Youch! I was thinking as much about flavour as any kind of contamination. Being reminded that the water I'm using has probably been in the pipes for a while calmed some of the contamination concern.

And 'DOH!' about doing the taste test. Why didn't I think of that