This is for you Zaffiro/Alexia owners. I picked up the habit (probably from here or CoffeeGeek) of flushing an ounce or two of water before each shot. This was supposed to eliminate the cooler water sitting in the pipes and brewhead.

But, when I had my machine over at Michael Teahan's shop last week for a rebuild, he asked why I was doing that. He pointed out that the first 1-1/2 oz. goes into the preinfusion chamber, not the coffee, and is automatically flushed out at the end of the shot. That made sense to me; so I stopped pre-flushing.

I do not detect any drop-off in shot quality, and I can go longer between tank refills. Thought this might be a useful tip.

Marshall wrote:This is for you Zaffiro/Alexia owners.

Also applies to double boiler machines.

The effect of a flush is machine geometry and flush volume dependent :

With a 10mm I.D. thermosyphon tube about 60mm long, there are about 50ml in the thermosyphon circuit.
With a 5mm I.D. thermosyphon tube about 60mm long, there are about 12ml in the thermosyphon circuit.

In all cases, the group will receive boiler temp water at the inlet and ~20°F cooler water at the group exit.

Depending on the boiler inlet and outlet points, the boiler mixing efficiency, sensor location, heater response and the interval since the last shot, the thermosyphon tube could receive almost room / pipe temperature water sitting in the bottom of the boiler if the return is to the boiler bottom. In our 12ml example, the shot tail temperature will drop like a stone. If the thermosyphon return is higher in the tank, the shot tail will rise. In our 50ml example, the effect is much less.

Marshall wrote:I do not detect any drop-off in shot quality

There could be several reasons for this Silliness aside, all rituals must be taste evaluated on an individual basis.

HB wrote:PS: It's a nit, but technically there isn't any water "sitting" in the pipes because of the thermosyphon.

"That portion of the water system which is nobly sacrificing its thermal energy to the brewhead whilst making its way from the boiler's exit pipe to its intake pipe."

Does anyone, by the way, know the rate of movement of the thermosyphon in a non-HX E-61 at a given outside temperature?

The flow rate will vary by a host of parameters :
Temperature differentials, pipe geometry, boiler pressure, scale, etc.

There is enough flow in the thermosyphon loop to create a geyser. Long ago, when I was learning how things worked, I thought to myself 'I wander how much water pumps through that loop' so I took the mushroom off my E61 machine (cold) and powered it up. A few moments later I had 200 degree water erupting from mount Isomac all over the kitchen.

cannonfodder wrote:There is enough flow in the thermosyphon loop to create a geyser. Long ago, when I was learning how things worked, I thought to myself 'I wander how much water pumps through that loop' so I took the mushroom off my E61 machine (cold) and powered it up. A few moments later I had 200 degree water erupting from mount Isomac all over the kitchen.

Was that an HX? How much of that might have been pressure in the boiler?

Dave, that was not flow, but simply the cold water expanding. Once the superheated thermosyphon expelled all water from the inlet tube, there would be no flow.

Yes, it will only bubble and spout water until the loop has run dry or equalized, but it was a rather interesting happening. It was several years ago bit I vividly remember it, as well as the gurgle/glug noise it made as the water spouted out of the group.

Another somewhat embarrassing moment was when I took the mushroom out of my newly set up two group. It was my first plumbed in machine. It did not dawn to me at the time to turn off the water. I loosened the group and cold water was trickling out. Thought it was odd but did not give it much thought. Put a plate under it to catch the drips but they never stopped. Then it dawned on me, mains pressure, turn off the water stupid. Made another mess, live and learn. Both machines were HX.