Correct. Measured at empty tank. To do that it's just enough to open a shut off valve that opens a drain downstream the tank with the pump off in order to bring the line pressure to 0 psi.
If you do not set the preset at a proper value you are not going to take full advantage of the bladder (or diaphragm). Let say that the tank is set at 8 psi (I see that most tank comes in that way, but some are at zero for shipping restrictions), and your pump works in the 60-40 psi range. You are going to fill the tank starting from 8 psi and the quantity of water that goes in before it reaches 40psi is never going to be used. Only the quantity filled between 40 and 60 psi.
If instead you set it at 40 psi, you start filling the tank at that pressure and then you are going to use all the water that goes in.
It may not make a huge difference, it's just a matter of making the system more efficient and reducing the number of times the pump has to refill the tank.

This is of course my understanding, but this video shows graphically what I mean, between 2:09 and 7:35 : Pressure Tank Comparison

I tested it and it is actually true, in my case. Since I am using the pump manually, I have preset the tank at 23 PSI, just above the pressure I want to use to refill the boiler. My draw down water is about 1.6 gallon,
However if I measure the draw down by closing the drain at 40 bars (when the pump restarts), it is only about 0.5 gallon. If I used the pump in automatic mode, I would have one gallon of water in the tank that is never going to be used.
I did not do a test it by presetting the tank at 40 bar, but I am sure that a good percentage of that one gallon would get in before the pressure reaches 60 bars, making the whole draw down water more than 0.5 gallon.


I see that most manuals specify that the preset pressure should be checked periodically. I may do it from time to time, but I think I that the second gauge I have installed, the one that measures the pressure at the tank, would allow me to see if it ever changes, by looking at what level the pressure drops very quickly, which means the tank is almost empty.
This is how I have it in this moment (left is the pressure at the tank, right is the pressure after the reducer). It's almost at that point.

If you have room in your line, maybe you can add a drain. I have used it several times, for other purposes as well.

userpix/35623_components_tank-pump_fina ... 3543RS.png

I made it long enough so that I can send the water back to the water storage container.
userpix/35623_watertank_hb1041WM.jpeg

Monte why is yours taking so long to fill? Manual mode? You're draining much of the water? Mine goes off 5-7 seconds every 2-3 days so I haven't been concerned with the exact pressure. Even if it goes off during a shot it doesn't seem to matter much with the Slayer. I can see why you might enjoy the refill process.

Your pump very fast, more than four times faster than mine. Mine is only 0.7 GPM and it has to deliver between 1-1.5 gallon, depending on when I turn it on. I thought I did not need more speed and I preferred to go with the quieter pump among the three I tried.

Regarding the need to change the preset pressure of the tank, It was more for the sake of the discussion, or in case, by having nothing better to do, somebody wanted to fine tune it .
I personally did it because when I began considering this system my impression was that the pump was the main think to think about. You have a delivery/demand pump feeding the espresso machine, and the accumulator tank is just an accessory to allow the pump to work in the right way. After using it I saw that it is almost the contrary. The pressurizes tank and the regulator are "the system" that feeds the Profitec. The pump is there to refill the accumulator when needed.

But what if yours is on auto. Maybe shorter refills more often. Is that good or bad. It may be that all parts are the system and the variable is the espresso machine. They all play a role and a very effective one.

I think that would be the right way. I would set the tank at 38 PSI and let it run in automatic. However as I explained before I prefer not to take the risk to flood the kitchen with more than the water that is in the pressurized tank, and I don't find having to turn the pump on manually inconvenient. Checking the pressure of the line when I go to to the espresso machine has become automatic as checking the temperature of the grouphead or the pressure of the boiler.

Considering a Londinium Compressa. Debating how to plumb it like a coffee cart. I don't have a water line near my machine location.

Imagining a water jug, pump, and variable pressure regulator direct into the machine. Plus tubing and a shut off valve

I have excellent filtered tap water already.

Looking at this pump + accumulator:

https://www.freshwatersystems.com/produ ... ost-system

For a water jug, have limited space, planning to find a 2 - 3 gallon model. Does the jug need to be sealed? Or does it need a vent? I've seen Caffewerks' pickup tubes, but that appears to result in a closed system.

The Compressa needs between 1.5 bar - 6 bar. Any recommendations on a variable pressure regulator that can go to 6bar/90 psi?

Anything else I'm missing? Really appreciate the discussion in this thread.

msg wrote:...
Anything else I'm missing?
...

A poster. At completion

My students would love it....... my wife would no longer be able to enjoy her espresso, LOL!