If the machine were connected to the mains I would have an accumulator (static tank) to regulate pressure.

malachi wrote:If the machine were connected to the mains I would have an accumulator (static tank) to regulate pressure.

My question is why a static tank plus flojet instead of a just a single pressure regulator?

You are right.
The FloJet is (in this case) due to the machine not being plumbed but rather run from a 5 gallon bottle.

malachi wrote:You are right.
The FloJet is (in this case) due to the machine not being plumbed but rather run from a 5 gallon bottle.

I see. When I first read about the concept in David Schomer's book I wondered immediately why he didn't just use a regulator. The only guess I have is a regulator will not prevent severe underpressure, which I assume is quite rare. It will only limit overpressure.

Keith

You don't want to merely limit line pressure. You want to instead control it. You want to eliminate any fluctuation in line pressure into the pump (in other words). Thus the Schomer solution or the static tank (air pressure accumulator) solution.

First a clarification for those who are following along...

Static tank: essentially a float valve keeping a tank partially full from which the pump draws water. Its purpose is to assure a constant inlet pressure.

Correct? And a comment... if one is that concerned about incoming micro-pressure variation, I would eliminate the pressure regulator if only to avoid the "valve chatter" as the flow rate slows, or a Flojet, which introduces its own pulses.

But this is definitely "extreme espresso gear" territory.

Two options:

Schomer Option - A tank with a float valve from which the pump draws water.

"Other" Option - A pressurized tank (usually using a bladder and air pressure) which provides positive pressure to the tank.

The goal of both is to isolate the pump from any fluctuations in inlet water pressure.

I would predict that neither are worth doing unless your pump is capable of producing non-fluctuating brew pressure (and you or the machine are capable of managing brew temp profile to be correct and consistent).

AndyS wrote:This would give you the ability to accurately "sculpt" the profile if you wanted the pressure to rise or decline during a shot.

What if, you hooked up some kind of "flowcontrol" pedal. Like an accelerator.
just a thought,
nick

PureArabica wrote:What if, you hooked up some kind of "flowcontrol" pedal. Like an accelerator

That would be nice, but I'd rather have a sensor hard-wired to my nervous system. That way, I could have the pressure ramp up and down using will power. I mean, why not?

Ooooohh... CREEPY!!
You could go all Sci-Fi with that! There could be a certain "breed" of people created just to extract perfect espresso with their minds.