# 'False pressure' Purging



## TomHughes (Dec 16, 2019)

Didn't even know I needed to do this.

Do I need to do it each time I switch the machine on and warm it up, or is it just after I fill the tank?

How do people get rid of air in the pipe leading in the group on the Pre-mill? I have been using the method of putting the steam wand on, then doing a few dry pumps of the lever, this seems to cause a load of bubbles to come out of the steam wand.


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## MediumRoastSteam (Jul 7, 2015)

Does your machine have a pressure stat? Does it have a anti-vac valve? Can you hear it shutting after warm up?


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## TomHughes (Dec 16, 2019)

MediumRoastSteam said:


> Does your machine have a pressure stat? Does it have a anti-vac valve? Can you hear it shutting after warm up?


 It just has a pressure release valve, no pressure stat.

I just switch it on on full power, wait till it starts releasing steam from the pressure valve and sitting at 1bar boiler pressure. 
Then do the false pressure purge which takes it down to 0.6bar, then switch it on to the 1 button, which is the low power. 
Then some dry humps to heat the group.


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## MediumRoastSteam (Jul 7, 2015)

TomHughes said:


> It just has a pressure release valve, no pressure stat.
> 
> I just switch it on on full power, wait till it starts releasing steam from the pressure valve and sitting at 1bar boiler pressure.
> Then do the false pressure purge which takes it down to 0.6bar, then switch it on to the 1 button, which is the low power.
> Then some dry humps to heat the group.


 Right. Sorry, I can't help you there. I don't know much about the ins-outs of that version of the machine. Sorry. 😞


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## TomHughes (Dec 16, 2019)

MediumRoastSteam said:


> Right. Sorry, I can't help you there. I don't know much about the ins-outs of that version of the machine. Sorry. 😞


 no worries!


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## GrowlingDog (Apr 10, 2016)

I switch on until it heats up to 1 bar, release the false pressure through the steam wand the same as you do.

I then lift the lever fully and let a bit of water run through the grouphead and basket. About 45g. This clears any air from the pipe.

I then remove the portafilter, put coffee in, tamp, reattach and pull a shot, leaving both switches on all the time until I start pulling the shot, at that point I usually switch it off completely as rarely make more than one espresso, and never use steam, if I am making another shot I switch it back to 1 to keep it warm until I am ready to pull the next shot.


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## BlackCatCoffee (Apr 11, 2017)

Are you actually getting false pressure? ie you open the steam wand for the first time since switch on you get some hissing and a bit of steam and the pressure falls off almost immediately to the point where you get no or very little pressure. Then it builds up to the correct level and is fine. If this is not the case then I would not worry.

I am not 100% familiar with Sage machines but if I am right in thinking they run on a thermoblock type arrangement I am not sure you can get false pressure at all. I could be wrong though.


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## Rob1 (Apr 9, 2015)

You'll need to purge the false pressure every time as the steam wand probably won't form a perfect seal as it's a metal on metal seal. There may be other potential air gets into the machine too. There are some interesting modifications to the Pavonis I'd look at if I were using mine again, mainly to the dipper tube on the syphon, blocking the group holes off (in the neck) and cutting a section out of the syphon at the bend to allow steam to escape. I don't think there's much point in releasing air from the tube and group aside from just lifting briefly before the shot.


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## Batian (Oct 23, 2017)

TomHughes said:


> It just has a pressure release valve, no pressure stat.
> 
> I just switch it on on full power, wait till it starts releasing steam from the pressure valve and sitting at 1bar boiler pressure.
> Then do the false pressure purge which takes it down to 0.6bar, then switch it on to the 1 button, which is the low power.
> Then some dry humps to heat the group.


 Are you sure about the pressure stat? It will look similar to the pic below (on my pre millennium Pro) mounted on undersides, or this:

https://www.theespressoshop.co.uk/en/La-Pavoni-Lever-Pressure-Switch---451308/m-2239.aspx


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## TomHughes (Dec 16, 2019)

Nope doesn't have that


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## TomHughes (Dec 16, 2019)

BlackCatCoffee said:


> Are you actually getting false pressure? ie you open the steam wand for the first time since switch on you get some hissing and a bit of steam and the pressure falls off almost immediately to the point where you get no or very little pressure. Then it builds up to the correct level and is fine. If this is not the case then I would not worry.
> 
> I am not 100% familiar with Sage machines but if I am right in thinking they run on a thermoblock type arrangement I am not sure you can get false pressure at all. I could be wrong though.


 Not a sage! Sage is gone. This is a la Pavoni


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## TomHughes (Dec 16, 2019)

Rob1 said:


> You'll need to purge the false pressure every time as the steam wand probably won't form a perfect seal as it's a metal on metal seal. There may be other potential air gets into the machine too. There are some interesting modifications to the Pavonis I'd look at if I were using mine again, mainly to the dipper tube on the syphon, blocking the group holes off (in the neck) and cutting a section out of the syphon at the bend to allow steam to escape. I don't think there's much point in releasing air from the tube and group aside from just lifting briefly before the shot.


 Which mods? I've seen ones which change the way the syphon works to mean you don't need the water boiling and providing pressure.


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## Rob1 (Apr 9, 2015)

If it sounds like the one I described that's probably it. There's a more invasive one too that involves routing a tube up from the heating element, going up through the base and into the neck of the group. I think it was called a hx mod or something, saw it on home barista.

https://www.home-barista.com/levers/fun-mod-to-pavoni-pro-t53907.html


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## Dave double bean (Mar 31, 2020)

I release some steam but the gauge doesn't drop much, I only installed it last week. I don't judge water through the head as it heats it up to much, just a few half pumps to get the temp to 80 85, then insert the porta and it rise slowly, temp build to 90 during preinfusion then to 95 as I pull the shot.

When I run water through the head I'm over 100° in a flash.

I no longer worth about false pressure as there doesn't seem to be any

Sent from my HD1913 using Tapatalk


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## MediumRoastSteam (Jul 7, 2015)

Dave double bean said:


> I release some steam but the gauge doesn't drop much, I only installed it last week. I don't judge water through the head as it heats it up to much, just a few half pumps to get the temp to 80 85, then insert the porta and it rise slowly, temp build to 90 during preinfusion then to 95 as I pull the shot.
> 
> When I run water through the head I'm over 100° in a flash.
> 
> ...


You don't have false pressure. Your machine has an anti-vac valve!


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## Dave double bean (Mar 31, 2020)

That's why the gauge doesn't move much, damn, and I thought I'd found a use for that gauge 

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## MediumRoastSteam (Jul 7, 2015)

😂 - There's no use for the gauge, apart from making sure your machine is at the pressure that you want it to be. Me.... I adjusted the pressure by mounting a gauge on the steam wand, so, every year, I check the pressure.... (and adjust it if I need to) 🙂 - It's a rather bulky addition to the machine, IMO. Doesn't serve much purpose. I can see the pressure profiling gauge being useful though, if that's your thing.


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## TomHughes (Dec 16, 2019)

On a different note I just installed a teflon gasket between the group and the boiler. 
Massive difference in heat stability! 
I can now get the group to a nice temp and hold it there, previously once it hit temp with dry humps it would continue to climb due to conduction from the boiler.


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