# Unequal water flow over IMS shower screen (Gaggia Classic)



## delatroy (Apr 18, 2018)

Hello.

I've purchased an IMS competition shower screen and brass group head replacement with a new seal however the flow over the screen is not that uniform.

I've tried flipping the group head gasket which had some affect. From seeing other videos, I see that droplets should show uniformly across the entire shower screen whereas I have columns forming as you can see:










I'm out of ideas on what I can do. I was thinking that it might be the OPV pressure but I'm not sure.

Any tips that I could try please?

Thanks in advance!


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## jj-x-ray (Dec 31, 2017)

Apart from adjusting the screw so the disc is not super tight or super loose, there's not much else. I suffer this too, but my coffee is fine which is all that matters.


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## delatroy (Apr 18, 2018)

jj-x-ray said:


> Apart from adjusting the screw so the disc is not super tight or super loose, there's not much else. I suffer this too, but my coffee is fine which is all that matters.


I see. It is quite tight. I will try loosen a fraction to see if it helps. How about the group head? I have that tight too. How about the water pressure? I'm yet to calibrate this to 9bar.

This, I guess, is what good flow looks like:


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## ashcroc (Oct 28, 2016)

delatroy said:


> Hello.
> 
> I've purchased an IMS competition shower screen and brass group head replacement with a new seal however the flow over the screen is not that uniform.
> 
> ...


How tight have you screwed it in? Try stopping just as the shower screen starts to flatten.


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## delatroy (Apr 18, 2018)

ashcroc said:


> How tight have you screwed it in? Try stopping just as the shower screen starts to flatten.


It was tight. Now I've tried about 10 different adjustments from barely on to tight. I think somewhere in the middle has improved things but not to the same consistency as the sample video. Is there anything else to adjust? Why does this happen on some machines and not others?

Could my water pressure be too high meaning that too much water is coming too quickly? If there's less water coming out, it would be easier to disperse across the shower screen.


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## El carajillo (Mar 16, 2013)

It is not unusual for the water to come through unevenly without the P/F and coffee in place. The pump cannot build up sufficient pressure when there is nothing there to form a resistance.

IF you could see it when there is a PF in place with a compressed coffee puck you would find it distributing evenly as the pump is working against a resistance.

Group seal should be in with inner chamfer + writing uppermost.


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## ashcroc (Oct 28, 2016)

delatroy said:


> It was tight. Now I've tried about 10 different adjustments from barely on to tight. I think somewhere in the middle has improved things but not to the same consistency as the sample video. Is there anything else to adjust? Why does this happen on some machines and not others?
> 
> Could my water pressure be too high meaning that too much water is coming too quickly? If there's less water coming out, it would be easier to disperse across the shower screen.


The vid you're comparing to is probably using a stock alu dispersion plate which has larger holes drilled into it. I've no idea how much of a difference if any that'd make once you have a loaded portafilter attached. Adjusting the OPV will do nothing until you reach the pressure it's been set at.


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## delatroy (Apr 18, 2018)

> Group seal should be in with inner chamfer + writing uppermost.


Sorry could you elaborate please?


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## delatroy (Apr 18, 2018)

Well for what it's worth, I reduced the pressure valve by one full turn and it hasn't had any affect


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## El carajillo (Mar 16, 2013)

The group seal (what the PF seals against) often has a slight chamfer on the inner edge (as do the seals for commercial machines) this is to accommodate the lip ,flange on screens for commercial machines. For your machine there may or may not be a chamfer on the seal, there is normally writing. The chamfer (if there) and writing should be uppermost when fitted.


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## El carajillo (Mar 16, 2013)

Adjusting the pressure without a gauge is a meaningless useless exercise. How do you know if the pressure is too high or too low.???


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## delatroy (Apr 18, 2018)

El carajillo said:


> Adjusting the pressure without a gauge is a meaningless useless exercise. How do you know if the pressure is too high or too low.???


Yeah I know but I heard that the Classic came stock at 12-13bar and that it's generally one full turn left to hit 9bar. I will get the pressure gauge kit next to calibrate properly but wanted to check if it had an affect on flow or not











> The group seal (what the PF seals against) often has a slight chamfer on the inner edge (as do the seals for commercial machines) this is to accommodate the lip ,flange on screens for commercial machines. For your machine there may or may not be a chamfer on the seal, there is normally writing. The chamfer (if there) and writing should be uppermost when fitted.


This is the group gasket that I have:









You can see it has writing on the side shown in the picture and a chamfer. On the other side, it's completely flat and has no writing. Currently.. the PF is sealing against the chamfer side and the flat side is sealing against the group head - is this correct? The original gasket had no chamfer - it was flat on both sides. I don't think this will have any affect on flow because the gasket doesn't interact with the grouphead or shower screen but I wasn't sure when fitting the replacement gasket.


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## ashcroc (Oct 28, 2016)

delatroy said:


> Yeah I know but I heard that the Classic came stock at 12-13bar and that it's generally one full turn left to hit 9bar. I will get the pressure gauge kit next to calibrate properly but wanted to check if it had an affect on flow or not
> 
> 
> 
> ...


Your gasket is the wrong way up. The flat edge should be in contact with the portafilter to create a decent seal. It won't have any effect on flow apart from potentially leaking when pouring a shot.

1 full turn of the OPV is a ballpark figure & could easily be, ore or less especially if you have a 2nd hand machine that you don't know the history of which may have been adjusted before. There's a thread on the gaggia section (might be the pay it forward section) with a portafilter gauge being passed around.


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## delatroy (Apr 18, 2018)

ashcroc said:


> Your gasket is the wrong way up. The flat edge should be in contact with the portafilter to create a decent seal. It won't have any effect on flow apart from potentially leaking when pouring a shot.
> 
> 1 full turn of the OPV is a ballpark figure & could easily be, ore or less especially if you have a 2nd hand machine that you don't know the history of which may have been adjusted before. There's a thread on the gaggia section (might be the pay it forward section) with a portafilter gauge being passed around.


Thanks I flipped it now. Should I be concerned with how the water is coming out of the screen or is that normal for the Classic?


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## L&R (Mar 8, 2018)

That is mine






These two give you cleaner group mainly.


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## delatroy (Apr 18, 2018)

L&R said:


> That is mine
> 
> 
> 
> ...


Squirting is similar to mine haha

I guess I'll roll with it and see how it goes thanks


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## JojoS (Oct 1, 2014)

I use the original Gaggia Classic screen together with the IMS. Solves the squirting problem.


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## AllezAllezAllez (Oct 23, 2018)

JojoS said:


> I use the original Gaggia Classic screen together with the IMS. Solves the squirting problem.


Over the top of each other?


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## JojoS (Oct 1, 2014)

Yes! The original then the IMS. Easy to compare the effect of double screen. Improved water flow and distribution is very obvious.


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