# Gaggia Classic - pressure, backflushing etc.



## Niggle (Nov 20, 2010)

Hi All

I've just move (up, I hope!) from a Gran Gaggia to a Gaggia Classic. The Classic is second hand, but barely used used, I'm told - that seems to be borne out by the general condition of the machine and the only slight staining of the filter holder, though the shower disc was a bit yucky. I gave it a descale and cleaned the group head, filter holder and shower disc with Puly Caffe.

The problem I seem to have is with the water flow rate - much faster than the Gran and much faster tha what appears to be the accepted norm. This is despite using Whittard espresso grind (much finer that the supermarket pre-ground I used with the Gran) and tamping hard (having acquired a nice, soild tamper). If I'm lucky, Santa might bring me a burr grinder so I can try beans - I gather Has Bean is a good supplier?

From my trawling, I gather pressure is a common problem and I'm tempted to try the POV adjustment that some recommend. So,:

1) Has any one here tried it? If so, is it as "easy" and effective and some say?

2) I will need to use a blind filter to check the flow rate which raises the next point. I tried using the rubber "perfect crema" device without coffee as a test and water flowed out between the filter holder and group head (I hope the correct term). When I put coffee in as well, coffee spat out from the same place. In both cases, I also had a water flow through the spouts. No problem when just using a filter. So,

(a) should I normally expect to see water flowing from above the filter holder when using the crema device or a blind filter - or is this an indication of excess pressure? My first guess would have been a faulty gasket, but I'd be surprised bearing in mind the supposed age and use of the machine.

(b) will adjusting the POV solve this?

© will this issue prevent me from judging water flow to adjust the POV and backflushing?

(d) will reducing the pressure affect backflushing?

Many thanks.


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## Glenn (Jun 14, 2008)

Welcome to Coffee Forums UK Niggle

Sounds like the grouphead gasket seals need replacing (even with low use these van harden over time, particularly if the portafilter has been left in the macine as it cools down

Easy to replace and cheap too (a few £ from Happy Donkey)

If there is not a good seal then pressure is reduced (easier for the water to escape via this route than to find its way through the coffee in the basket)

Try this before adjusting the OPV


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## KRW (Aug 5, 2010)

Don't mess about with the pressure until you've had a go with a good grinder. I had exactly the same issue - no matter what preground coffee I bought, it would shoot out of there - but since getting a decent grinder its been absolutely fine. No trouble getting amazing tasting 20-25 second shots. From what I have read, fresh beans have oils and the like that won't be present in pre-ground no matter how finely its been ground. This adds resistance to the water and prevents a 'gusher'.


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## Niggle (Nov 20, 2010)

The blind filter arrived today - so I tried a backflush with it anyway. I was surprised that the leakage was less than I expected and it did seem to backflush OK. I was also surprised how much dirty looking water came out! Not loads, but still more than I expected - shows what could accumulate over longer time.

I'll keep an eye on the gasket - it doesn't feel hard from poking it, and from the results of the backflushing experiment I wonder if much of the problem is that the filter holder just doesn't fit very well with the rubber crema device in it - just as well I don't intend using it if I can avoid it.

Interesting about the grind - I will wait and see what happens when I can grind my own beans before trying something more complicated.

Thanks again.


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## KRW (Aug 5, 2010)

Heh, if you look through the threads, I'm sure you can find a post from me asking the same thing. I was convinced the pressure was too high. I'm very relieved I didnt try that mod.

I would, however, strongly recommend changing the steam wand. That's a fairly straightforward mod and the difference it makes to steaming is astounding.


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## Niggle (Nov 20, 2010)

Thanks KRW.

I can't wait to see if I can get a fine enough grind to produce a 25 sec shot.

As it happens, I have already changed the short pannerello wand for the longer one so that without the outer sleeve it acts like an extended bare wand and I have to say that seems to work fine - much better than the original which went a bit overboard! I didn't want to go the whole hog and completely change the metal wand. On the Gran, I removed the pannerello completely, but used a small (300 ml) jug which I now find much too small.

I found another thread here which enabled me to gauge the age of my machine. Rather older than I thought, but it's still clear that it hasn't been used that much. However, in view of this I have ordered a replacement group head gasket on the basis, as Glenn said, that it can deteriorate over time even with little use.

The Classic came with a milk thermometer which I have to say I have found most useful as it is now clear that previously I was overheating the milk. Every tweak seems to make a difference ...


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## Glenn (Jun 14, 2008)

Niggle said:


> ... Every tweak seems to make a difference ...


Thats the key to coffee. Once you have one variable sorted, move onto the next, and progressively get better and better.

Sounding positive!


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## lowfer (Nov 20, 2010)

Hi There, i am a relatively new classic user, one thing i would double check on is your basket. I would highly recoment an unpressureized if you haven't got one. Have a look at the base of the basket, if their is only a small ring about the size of a 2p on the back then you have a pressurized. The unpressurized has holes all over.

I have used both and the pressurized squirted coffee all over my kitchin, the unpressurized gives me great Crema but a bitter taset, i am currently working on this at the moment.

You canget an un-pressurized basket from Happy Donkey for about 6 quid i think

best of luck LOWFER


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## gaggiamanualservice.com (Dec 22, 2009)

hi, i would not recommend adjusting the opv, this is set at factory and rarely needs altering, experiment with diferent grinds and techniques as more harm can be done than good if you get too much pressure, the pump is vulnerable if over pressure

mark


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## Niggle (Nov 20, 2010)

Thanks, all.

I replaced the gasket - and found the existing one to be dented, I do wonder if the portafilter had generally been left in place whilst not in use as there wasn't that muck when I removed the bits to get at the gasket. Leak stopped and portafilter fits fine - I had read of people having problems with what sounded like thicker gaskets so the portafilter wouldn't fit properly. Got the gasket from good old Ebay - cheapest I could find and advertised as an official part ...

I have the normal unpressurised basket, Lowfer. The rubber crema device came with the Gran and I am trying to avoid using it.

With regard to the pressure, GMS, my idea was to reduce it rather than increase and thus slow down the flow through the coffee. However, I will certainly wait and see if I can improve matters with a better home-grind (if Santa can make it through al the snow...) - as people have said, the pre-ground coffee does not seem to be anywhere near fine enough (trying to cope with too many types of coffee machines, I guess) - though if somebody knows of a readily available suitable pre-grind ....

Cheers


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