Water Pressure Regulator Tips

la marzocco, synesso, simonelli, cimbali etc

Water Pressure Regulator Tips

Postby Greg H on Wed Jan 13, 2010 1:55 pm

Hello Coffeed Community, this is my first post. I've read and used your collaborative insights for a couple years now and I consider it a great privilege to join the conversation.

We recently added a water pressure regulator to our 2 gr Linea Paddle. It is a part by Grainger seen here http://www.grainger.com/Grainger/items/5AJ81?Pid=search

Roger from La Marzocco pointed us to these and I'm curious to read what this community considers to be the benefits?

I've talked to some folks and they are running their line pressure at 30psi.

Has anyone deduced any general results for different psi numbers , or any observations regarding how different line pressures interact with different doses and roast levels to affect flavors?


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Re: Water Pressure Regulator Tips

Postby Jason Haeger on Wed Jan 13, 2010 8:33 pm

I could be wrong, but from what I understand, all that line pressure controls is "pre-infusion" time before the pump is activated. Once the pump is on, it shouldn't make any difference unless the pressure is irregular.

Which brings the question from line pressure about time instead of pressure.
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Re: Water Pressure Regulator Tips

Postby nick on Wed Jan 13, 2010 9:38 pm


You probably know, espresso pumps are generally booster pumps, not sump pumps, so they're gonna need a decent amount of inlet pressure. With the Marzocco paddle groups, the mechanical valve will open the group head to the line pressure, progressively increasing in aperture until it's all the way left, which activates the pump. This control allows for some progressive control over the pre-infusion, or the initial pressure ramp-up.

Too often, the incoming water has some pressure fluctuations, in which case a pressure regulator could help (an expansion tank would be even better).

Aside from that, I'm personally not a big fan of that type of pre-infusion. Most of the popular espresso machines on the market, including Marzoccos, feature a flow-restrictor somewhere in the group plumbing, which if placed in a useful spot, results in a progressive increase in the pressure within the extraction space. That pretty much accomplishes what pre-infusion is trying to do, and in a more consistent and reliable way. I tried for years to achieve better tasting espresso by using the line-level preinfusion with our Synesso, but that machine has heavy flow restriction too.

That said, I know that this is a debatable point. I just haven't personally experienced the benefits, despite trying.

Don't get me wrong: I LOVE paddle-actuated groups, and I'll totally buy machines with paddle groups in the future. They're much better (read: more fun) than rocker switches or buttons… but it's still about "on-off" for me.
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Re: Water Pressure Regulator Tips

Postby Greg H on Thu Jan 14, 2010 9:47 am

Thanks for your thoughts Jason and Nick.

The reason we've been checking out the regulator stems from my visits with Mark at Synesso and someone from Four Barrel who was pulling shots at the Marzocco booth during coffeefest Seattle.

Mark seemed to be hinting that the next area of development for espresso machines and extraction is in the realm of line pressure regulating and greater pump pressure control. He was doing some interesting things with pre-infusion, pump activation, back to pre-in fusion that had some noticeable effects on color at the end of the shot.

The chap from Four Barrel mentioned that they put all their machines at a certain number psi, and from that I interpreted that in their choice of numbers, they noticed some type of effect on flavor profile? Or maybe it just has to do with better functionality for the machine?

Maybe someone from Four Barrel could chime in and clarify for us?

All of this got me thinking: is the Rao thesis correct? Does pre-infusion only make the shot a bit more forgiving for inconsistent distribution and tamping technique? Or is there really something to what these folks are buzzing about regarding line pressure and effect on flavor?

Thanks again for your interaction.

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Re: Water Pressure Regulator Tips

Postby naznar on Thu Jan 14, 2010 11:32 am

Setting your regulator lower puts more strain on your pump. Since the pump is boosting line pressure, a lower line pressure will make the pump work more to achieve the same output.

With flow-restrictors (jets, gicleurs) built into the machine, usually close, or at the brew valves themselves, the pressure of incoming water will still affect how fast the cavity above the puck fills, and then how fast water pushes through the puck. With a pump machine a higher line pressure might reduce flutter caused by the vanes, this is just a theory.

We set our line pressure at 25psi at the resulator with a spring lever 1980 san marco, and our flo-restriction within the machine to roughly .8mm-1mm. We were trying to time up our shots to drop out of the spouts at 8 seconds with a total time of 25-28 seconds from opening the water valve to pulling the demitasse. Basically it just took too long. We FELT it took longer, and we also FELT the shots were not as good. We are pretty experienced with this type of machine. We have since turned the regulator up to 45psi and everything got better. I like the speed of a higher line pressure, but still want it relatively low.

I would disagree that an accumulator tank is better, they do different things. A regulator will set the pressure while also softening flutter in the line dramatically. An accumulator will cushion the line pressure but not alter it. It seems like the best system would include both of these techniques. Water line pressure will vary dramatically from building to building within a city based upon the buildings regulator and perhaps upon the city's distribution system. I do believe that line pressure makes a difference if you are using it without a pump. Being able to standardize line pressure has helped us a ton for reference.
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Re: Water Pressure Regulator Tips

Postby Greg H on Fri Jan 15, 2010 8:56 am

In response to Nick's comments on flow restrictors I e-mailed Roger at La Marzocco to ask him how flow restrictors affect line pressure.

Here is his response:

"The restrictors do reduce the effect of the regulator. Even with a flow
restrictor a regulator gives you more control over the rate of preinfusion
that I find useful. At some point the differences in adjustment become
difficult to discern. The regulator is most useful if you have high (>
60psi) incoming line pressure."
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Re: Water Pressure Regulator Tips

Postby James Hoffmann on Sun Jan 17, 2010 10:35 am

From what I understand of line pressure preinfusion - the goal is to completely saturate the cake with water before full pressure is exerted upon it.

The required pressure is related, to some extent, to your dose. With 14-16g doses and mid twenties brew times then 2 bars can be enough to saturate the cake (approx 30 psi) but I've found that if you want to use a larger dose, or pull a relatively slow shots then you need more pressure to get the job done. This has been playing on a Arduino lever (where you get line pressure through an HX, rather than boiler pressure) and on a Synesso. I need to boost up my line pressure because at the moment it is a little low.

What I haven't done, but will later today, is look at how long it takes my Synesso to get up to full pressure on a Scace 2, and then pull a naked shot and see how saturated the cake gets in that time.
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Re: Water Pressure Regulator Tips

Postby Luke Shaffer on Fri Jan 22, 2010 11:07 am

Greg, thanks for the tip on the regulator. We have steady but high pressure at one of our locations and I've had this on my "to-do" list for some time. This seems like a simple enough solution.
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Re: Water Pressure Regulator Tips

Postby Marshall on Fri Jan 22, 2010 12:26 pm

As an amateur barista who only pulls about four shots a day, I normally refrain from posting in the technical threads here. But, I recently installed an LM GS/3 paddle at home and consulted my friend and pressure-profiling guru, Greg Scace, about setting the line pressure.

Greg recommended setting my regulator at 45 psi, and I have been very happy with that. At that setting, line pressure preinfusion takes from 6-12 seconds (depending on grind and volume) to saturate the puck and start to drip from the spout.
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Re: Water Pressure Regulator Tips

Postby justinemerson on Mon Jan 25, 2010 2:18 am

hi All,
for what its worth we set our line pressure regulators, regardless of machine, to around 3 bar. The preinfusion is only apparent when you activate the first group on most machines, if the pump is running the entire system will be at pump pressure. We find the most benefit when we cant get a clear line to the machine ie if there is a dishwasher, water chiller, etc on the same water supply. A good pressure reg will negate the effect of someone decreasing the incoming water pressure by turning on a tap or something. But we have found preinfusion can do some quite dramatic things to the coffee's flavour profile. Without it on the la san marcos the coffee pours a little more inconsistently and the shots are a lot more thin, flat and unbalanced. funnily enough on the slayer a real long slow infusion works a lot better for origins than any of our blends, bringing up a lot more dimension, acidity and body while almost always delivering a really balanced cup. our blends seem to like a short sharp infusion then straight up to pump pressure. good fun experimenting 'tho.
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