I have a direct connect Bezzera Strega I'd originally planned to plumb in, but at the moment I'm running it connected to a Flo-Jet bottled water system. For whatever reason, this seems to produce inconsistent shot timings. The pump pulses on and off randomly during pre-infusion, and its pressure switch is not triggered very well by the boiler fill solenoid (I can hear it click, then the pump laboriously pulses on and off in tiny bursts, causing one of the boiler valves to whistle).

I have a small Shur-Flo accumulator tank I've tried using with this system, but it introduces its own set of problems. It came pre-pressurized to only 20 psi, which is really too low for pre-infusion. It's also quite a small tank, which means it empties quickly with all the HX flushes, making the pressure dip and triggering the Flo-Jet a lot (which spikes the pressure).

Something I've always been unclear about with accumulator tanks is that there must be a pressure drop as tank empties, before the pump is triggered to re-pressurize it. Surely this, along with the spike when the pump turns on, negatively impacts pressure consistency unless there is a pressure regulator on the inlet of the machine set lower than the tank.

I see a lot of people talking about running their accumulator tanks at 40 psi. This is the maximum rated pressure for the bottled water Flo-Jet model. I have no idea what the pressure switch is set to, and there doesn't seem to be any way to adjust it.

What are my options if I want a rock-steady pressure for pre-infusion? I know significantly larger accumulator tanks are available, but I don't know how high I can pressurize a tank and still use the Flo-Jet. Do I want some sort of regulator on the machine itself?

Im about to set up a machine on a Flojet system as well and have been wondering about accumulator tanks as well, but can't find any info as well. If anyone out there can enlighten chris and myself it'd be greatly appreciated.

Chris, where did you get your shur-flo tank from? any Canadian retailers sell accumulator tanks?
thanks
Alex

mindless_fool wrote:Chris, where did you get your shur-flo tank from? any Canadian retailers sell accumulator tanks?

I'm using this 24oz Shur-Flo accumulator tank, which I've seen recommended for home espresso machine use a number of times. The actual water capacity at pressure is more like 2-4oz; the higher the pressure, the less water it holds.

I see EP sells larger accumulator tanks, and also typically pairs the small accumulator with what seems like a more capable pump than the Flo-Jet. In some configurations they provide the accumulator pre-charged to 20 psi like mine is, while in others it is higher.

No matter what the pre-pressurization level, a small accumulator must be emptying for practically every shot, especially when an HX flush is required. This means random pressure drops and spikes from the pump re-filling, which get transferred straight to the machine's inlet.

Presumably some sort of pressure regulator on the inlet of the machine set below the trigger level of the pump would completely smooth out any pressure differences, but I've never seen much discussion of this. I am also unclear on how much I could raise the pressurization of my accumulator before it would make its function redundant by leaving the pump constantly running in use. The max pressure of the Flo-Jet itself is only 40 psi, which is pretty much where I'd like it for pre-infusion. Perhaps I need to look at a higher end pump/accumulator system for this?

Thank you for the link Eric, but I have read your replies in that thread many, many times while searching for info over the last year. I actually made quite a few posts in the thread myself when I was considering what to buy.

I'm not really sure what to take away from your replies in the thread, because I've asked some specific questions I don't see answers to there. Your suggestion to use a large accumulator pressurized to only 6-7 psi to get a good amount of accumulation seems reasonable for pump machines that don't use line-level pre-infusion. My Strega does not have a pump, so it depends entirely on the line pressure for pre-infusion and boiler fill operation. 7 psi would not provide any meaningful pre-infusion; it's not even enough pressure to fill the boiler.

Basically, I am looking for a way to get 2-3 (preferably 3) bar of very stable line pressure from a bottled water system. A large accumulator eliminates the frequent pump fills with the small tank, but there is still a dip from the nominal pressurization as the bladder expands, followed by a spike from the pump when the pressure switch is triggered. I guess this is just accepted as a matter of course by most users? The other issue is that the Flo-Jet cuts out at only 2.8 bar, so it's impossible to me to get the 3 bar line pressure through an accumulator unless I buy a different pump.

I would have thought that a regulator installed after the accumulator and set below the pump's pressure switch level would smooth out everything, but you seem to be saying regulators don't work properly for this sort of thing. Is that the case?

erics wrote:That's not how an accumulator works - it gets pressurized to the cut-out value of the flojet. I think 40 psi is their spec but I have measured 36 - no big deal. A 2 gallon accumulator, a tee at the top port, a nice gage, and you're on your way.

That's where the $50 vibe pump comes in handy. I'll have to re-read that thread because I would hope that I did not say that about a pressure regulator. A pressure regulator needs to be properly sized for the desired flow (and pressure range). Watts makes a nice one - http://www.watts.com/pages/_products_details.asp?pid=3428

Thanks for correcting me, I'm not really sure why I was thinking

So, basically, the system pressure fluctuates between the trigger and cut-off pressure set points of the pump. For the basic water bottle Flo-Jet I guess that is between 30 and 40 psi (2.1-2.8 bar). For some of Shur-Flo's other consumer pumps with more detailed specifications, they talk about pressure ranges of up to 1.4 bar (!). Surely even a 0.7 bar fluctuation is detrimental to shot consistency? If I install a small regulator after the accumulator, set below the trigger level of the pump, will it eliminate the pressure fluctuations to a large degree?

Home Depot sells this 2 gallon Flotec accumulator. Is it the sort of thing I am looking for? CC sells a pressure regulator/gauge combo with John Guest fittings pre-installed for about $40, which I assume is appropriate for this sort of thing (correct me if I am wrong). What sort of pump would I want to use to get everything above 3 bar (you mention a vibe pump...)?

Don't mean to hijack the thread but how would you hook up that 2 gallon tank?

I will see if I can buy the Watts regulator from a Canadian supplier. It seems like I'd want the 1/4" fittings with 0-60 psi gauge.

Ordering little parts like this is in Canada is an exercise in frustration. I can see the part on Watts Canada's site, but I can't buy from them. I can get a list of regional distributors that carry that line of products, but I can't buy from them either as an individual. So that leaves me with... Home Depot (which barely stocks anything), or calling around to local plumbing supply places that probably don't carry that specific part anyway. This is something that happens every time I want any specialty item, because small companies in Canada have zero online presence, while there are probably hundreds of little places I could order it from down there.

Oddly enough, Amtrol Canada's office is only 25 minutes from where I live. Should I go out of my way to buy one of their 2 gallon RO tanks rather than the Flocon tank I linked (again, Home Depot only easy source...)?

The vibe pump you linked would require extra components like a pressure switch to be used of this sort of thing, wouldn't it? Shur-Flo and other companies make higher pressure diaphragm pumps with adjustable pressure switches that aren't too expensive. A drop-in solution would certainly be my preference.