# Gaggia Classic, problem with backflushing



## Hampus (Sep 20, 2020)

I have a 2005 Gaggia Classic bought second hand in 2010. During the years it it has seen light use until this spring when lock-down caused it to be upgraded to daily use.

With the increased usage I felt the need to learn more about maintaining the machine and noticed that back-flushing this machine does not work as it should.

The problem is that when backflushing the machine with the blind filter, after turning off the coffee switch no water flows through the drain pipe and the portafilter remains under pressure. (Trying to remove the portafilter from the grouphead requires a lot of force and when it eventually comes loose, water sprays in all directions.)

Making coffee works fine, but with wet pucks. Water flows as normal from boiler to grouphead.

After some research here, my guess was that the three-way solenoid was the source of this problem. If the valve was stuck in the down position causing water to flow only between the boiler and grouphead, but not to the drain pipe, then that would explain what I'm seeing.

I followed the instructions on this post to remove the solenoid valve. I then opened it and cleaned it by soaking in descaler.

Now, there's a few reasons why I think the solenoid valve is working as intended:



With the solenoid valve cleaned and removed from the machine, i tried to pour water in the bottom left hole and could see that water did run though the valve and exited though the top part as expected when no electrical current flows though the solenoid. Seems promising.


When the valve was fitted back on the machine, I deliberately did not attach the electrical wires to the solenoid to see if it would let water from the boiler into the group head (which it should not if the valve seals properly). When I flipped the coffee switch I could hear the pump working, but no water came out of the group head. So far so good.


Finally with the wires reattached to the solenoid, water flows from the boiler down though the group head.


This makes it seem to me that the solenoid valve works as it should.

But, the water still does not come out though the drain pipe!

Now, I'm contemplating whether I should disassemble the boiler and grouphead to see if there is something stuck somewhere in there preventing the water to escape though the drain pipe, but I can't think of an explanation to how water could be able to go into the grouphead, but not escape it to the drain pipe if the solenoid valve was working. (As far as I can tell, it's using the same pipes, so if water can enter the grouphead it should be able to leave it when backflushing.)

I have also considered just buying a replacement solenoid valve, but I'm hesitating to spend the money since I can't find a problem with the old one.

Any suggestions on what I should try next?


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## Blue_Cafe (Jun 22, 2020)

:classic_ninja:


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## MrSmartepants (Aug 3, 2020)

This may sound like a dumb question, but are you partially filling the portafilter with water BEFORE latching it into the grouphead?

The reason I ask is because the first few times you backflush on an empty portafilter, it's just sucking air out. Water doesn't come out of the waste pipe (for me) until around the 5th backflush.


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## MediumRoastSteam (Jul 7, 2015)

MrSmartepants said:


> This may sound like a dumb question, but are you partially filling the portafilter with water BEFORE latching it into the grouphead?
> 
> The reason I ask is because the first few times you backflush on an empty portafilter, it's just sucking air out. Water doesn't come out of the waste pipe (for me) until around the 5th backflush.


 Something is not right with your machine then. Because, whether you fill with water before locking the PF or not, the pump will fill the blind basket up with water. If you are not getting water through the solenoid and down the drip tray, then you might have a blocked solenoid? Which Gaggia Clsssic have you? Which year?


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## MediumRoastSteam (Jul 7, 2015)

Hampus said:


> I have a 2005 Gaggia Classic bought second hand in 2010. During the years it it has seen light use until this spring when lock-down caused it to be upgraded to daily use.
> 
> With the increased usage I felt the need to learn more about maintaining the machine and noticed that back-flushing this machine does not work as it should.
> 
> ...


 When you brew coffee normally, is he pressure released? If that's the case, the valve is working, but doesn't explain the issue you are having when backflushing though.

With machine off, try to attach a silicone hose to the drain pipe and blow air in (with your lungs). Any blockages you can feel?air should flow normally back through the group.


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## Hampus (Sep 20, 2020)

I never tried to fill the blind basket with water before when backflushing, but I tried it this morning. Doesn't seem to make any difference though. I tried flushing six times, 10-15 seconds. Still no water though the drain pipe.


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## Hampus (Sep 20, 2020)

MediumRoastSteam said:


> When you brew coffee normally, is he pressure released? If that's the case, the valve is working, but doesn't explain the issue you are having when backflushing though.
> 
> With machine off, try to attach a silicone hose to the drain pipe and blow air in (with your lungs). Any blockages you can feel?air should flow normally back through the group.


 I think the pressure is released as it should when brewing coffee. Removing the portafilter is not that hard. Nowhere near as hard as removing the it with a blind basket.

I tried to attach a hose to the drain pipe and blow air in. Wasn't sure at first if I could feel anything coming through the group but after removing the shower screen I could definietly feel air coming through, so nothing's blocking there.


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## MediumRoastSteam (Jul 7, 2015)

Hampus said:


> but after removing the shower screen I could definietly feel air coming through, so nothing's blocking there.


 When backflushing, and when you remove the PF at the end, has the soap been dissolved? Have you checked for blockages in the dispersion plate or shower screen?


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## Hampus (Sep 20, 2020)

MediumRoastSteam said:


> When backflushing, and when you remove the PF at the end, has the soap been dissolved? Have you checked for blockages in the dispersion plate or shower screen?


 I removed the shower screen and dispersion plate this morning and they do not appear to be blocked.

I have been backflushing with dishwasher powder and when I remove the PF the powder is typically not dissolved. I imagine there's a risk of some of that powder being sucked back and causing a blockage but I can not see any signs of blockage here.


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## Agentb (Feb 11, 2017)

Hampus said:


> I have been backflushing with dishwasher powder and when I remove the PF the powder is typically not dissolved. I imagine there's a risk of some of that powder being sucked back and causing a blockage but I can not see any signs of blockage here.


 The two holes holes in the solenoid are tiny and the solenoid valve needs to move freely. It sounds to me you have not cleaned them all or there is some downstream blockage. If you haven't serviced the boiler and group since owning, that might not be a bad idea, after all it's 15 years old!

There is a reasonable description here https://usermanual.wiki/Gaggia/Classic3WaySolenoidCleaning.2032645276/view and here http://www.gaggiausersgroup.com/index.php?action=ezportal;sa=page;p=67

My back flushing with cleaner is once a week or two i guess, and only after i have removed, cleaned and replaced the shower head and block. then some Purly or Cafiza, no more than a quarter of a teaspoon and hot water, and make sure it has all dissolved with no solids in the blank basket before locking in. This reduces the risk of cleaner blocking those little holes.

Good luck! 👍


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## MrSmartepants (Aug 3, 2020)

Hampus said:


> I have been backflushing with *dishwasher *powder


 😨 I'm pretty sure that's your problem right there! You should only be backflushing with descaler (Puly, Cafiza, etc.), *NOT detergent*.


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## MediumRoastSteam (Jul 7, 2015)

MrSmartepants said:


> 😨 I'm pretty sure that's your problem right there! You should only be backflushing with descaler (Puly, Cafiza, etc.), *NOT detergent*.


 Those are not descalers! Those are coffee machine detergents!


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## MrSmartepants (Aug 3, 2020)

Sure, OK. But the point is that *dishwasher *detergent is designed for dishwashers and using it in an espresso machine MAY cause the unintended problems the OP is encountering.

What products SHOULD the OP be using to backflush?

And my box of Puly says clearly on the front "descaler".


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## Blue_Cafe (Jun 22, 2020)

Hampus said:


> I have been backflushing with dishwasher powder


:classic_laugh:​


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## Blue_Cafe (Jun 22, 2020)

MrSmartepants said:


> What products SHOULD the OP be using to backflush?


 According to Gaggia, you shouldn't.

There. i said it.


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## ratty (Sep 22, 2019)

For descaling;

https://www.ebay.co.uk/itm/Puly-Caff-Calcinet-Descaling-Descaler-Crystals-1-Kilo-Tub-for-Coffee-Machines/153104644654?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649


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## Blue_Cafe (Jun 22, 2020)

ratty said:


> For descaling;
> 
> https://www.ebay.co.uk/itm/Puly-Caff-Calcinet-Descaling-Descaler-Crystals-1-Kilo-Tub-for-Coffee-Machines/153104644654?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649


 https://www.maxicoffee.com/en-gb/puly-caff-plustm-powder-espresso-machine-cleaner-370g-p-2345.html#:~:text=Puly Caff is not advised,basket and aluminium porta filter.

*Std Puly Caff. See post below for further details.


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## ratty (Sep 22, 2019)

Puly Caff Calcinet is a different product than Puly Caff!


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## Rob1 (Apr 9, 2015)

Fairly certain ordinary Puly Caff is not recommended for use on aluminium either. I thought the Gaggia had a brass group and portafilter with steel baskets?


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## L&R (Mar 8, 2018)

Adjust your pressure to 9 bar static and this effect will disappear. Now you are probably at 15bar and 3way blocks when backflushing.


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## Blue_Cafe (Jun 22, 2020)

ratty said:


> Puly Caff Calcinet is a different product than Puly Caff!


 https://www.pulicaff.com/docs/br_calcinet-eng.pdf

Correct. One is for washing machines, the other for espresso machines.

Well,

Reading the MSDS:



> Descaling powder for espresso coffee machines, dishwashers, heat exchangers. Do not use for purposes other than those stated Uses advised
> 
> Contents:
> 
> SAFETY DATA SHEET CALCINET Polvere CALCINET_EN_20150422 Page 2 of 5 Substances CAS n° Acute oral toxicity, rat REACH Reg. n° 1999/45/EC Content Classification EU-CLP EC 1272/2008 Sulfamic acid 5329-14-6 LD50 => 1600 mg/kg 01-2119488633-28 80-90% Skin irrit. 2 H315 Eye irrit. 2 H319 Aquatic chronic 3 H412 *Citric acid* 5949-29-1 LD50 = 11700mg/kg 01-2119457026-42 <5% Eye irrit. 2 H319 Tartaric acid 87-69-4 LD50 2000/5000 mg/kg 01-2119537204-47 <5% Eye Dam. 1 H318


 Puly Caff notes that



> Avoid contact with humidity, strong acids, thin aluminium.


 I would just stick with the Gaggia stuff tbh


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## J_Fo (Dec 24, 2017)

Tidied to keep on topic


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## Blue_Cafe (Jun 22, 2020)

Actually, after some further research, descaling is a bit of a black art when it comes to aluminium.

note that the Gaggia boiler also has chrome, copper and brass in it as well.

Puly Caff is out, as are a lot of other descalers, which advise against aluminium. Calcinet is a bit of a mystery, as it is sold for washing machines. I've no idea why Puly think to change the formulas for application but perhaps it doesn't have oil dispersants in it ( i dunno).

I'd stick to the Gaggia/Philips stuff. It is apparently balanced to not be corrosive to the inners of the Gaggias. (certainly uses different formulas).


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## Hampus (Sep 20, 2020)

L&R said:


> Adjust your pressure to 9 bar static and this effect will disappear. Now you are probably at 15bar and 3way blocks when backflushing.


 Interesting!

I had actually planned to adjust the pressure to 9 bar on this machine. (I ordered a pressure gauge last week but it hasn't arrived yet&#8230

I have read about "blind OPV adjustment" by simply turing the OPV counterclockwise 270 degrees. But since I am not the original owner I did not know if the OPV was still in the factory setting. The previous owner had replaced the steam wand with a Rancilio Silvia wand so perhaps they had adjusted the OPV as well.

Anyway, today I read about the "glass of water" approach to estimate the pressure from the OPV output flow rate. Trying this on my machine I concluded the the OPV had probably not been modified since the flow was 60 ml in 30 seconds suggesting a pressure greater than 12 bar.

Knowing that I'll soon have a pressure gauge, I figured I might as well try to adjust the OPV to see if it had any effect on the solenoid. After turning the OPV counterclockwise 270 degrees the flow was 110 ml in 30 seconds, which according to the link should be close(r) to 9 bar.

When running the machine with the blind filter to measure the flow rate, I had some initial success. After switching off the coffee switch, I did finally see a flow of water from the drain pipe and the portafilter was for the first time easy to remove, indicating a successful pressure escape though the solenoid valve!

The joy was short-lived however when I was unable to reproduce the behavior on later backflushing attempts. Each time after that, the result was the same as before: no water in the drain pipe and the portafilter hard to remove because of the pressure inside.


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## Hampus (Sep 20, 2020)

Agentb said:


> The two holes holes in the solenoid are tiny and the solenoid valve needs to move freely. It sounds to me you have not cleaned them all or there is some downstream blockage. If you haven't serviced the boiler and group since owning, that might not be a bad idea, after all it's 15 years old!
> 
> There is a reasonable description here https://usermanual.wiki/Gaggia/Classic3WaySolenoidCleaning.2032645276/view and here http://www.gaggiausersgroup.com/index.php?action=ezportal;sa=page;p=67
> 
> ...


 I did one more disassembly of the solenoid valve this evening, checking again for blockage. (Forth time this week  )









Last time I took it apart I did more or less as suggested here. (Soaked it in detergent for 20 min/rinsed/soaked in citric acid solution for 20 min/rinced. Cleaned the top hole with a needle..) Now when taking it apart everything still looked clean.









Top part seen from below, no blockage here!









The only potential problem I could find was the rubber knob on the top of the piston. It has been worn down in the center, creating a small grove. It can still seal the hole in the top part, but I wonder if perhaps this could cause the piston to become stuck in the top position after the piston is engaged by the solenoid, blocking the path to the drain pipe. At least that would explain the behavior I'm seeing.

Anyway, the piston moved freely and did not get stuck when I pushed it with my fingers.









Once assembled again, I could check that water could run freely from the bottom left hole (which would be attached to the group head) and out the top hole (which would be attached to the drain pipe).

Since I was able to blow air though from the drain pipe back though the group head though the solenoid valve, I don't think there is any downstream blockage.

My best guess is that the piston gets stuck in the top position after the solenoid is engaged during the brew and then remains in this position, preventing the backflush drain. Just wish I had some way of verifying this.


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## Hampus (Sep 20, 2020)

Thanks a lot for all the suggestions on cleaning products! I now realize that putting dishwasher detergent through the grouphead and solenoid is not a good idea.

Having disassembled the solenoid valve and knowing the size of the holes inside I understand that using any detergent with large crystals that does not immediately dissolve on contact with hot water in the portafilter could easily become stuck in the small holes of the solenoid valve.

Anyway, I will make sure to get the suggested products. In the meantime when testing I'm only backflushing with water.


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## Blue_Cafe (Jun 22, 2020)

Have you tried hitting it with a hammer?

May or may not work but it should make you feel better.


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## Hampus (Sep 20, 2020)

Blue_Cafe said:


> Have you tried hitting it with a hammer?


 Tempting


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## Agentb (Feb 11, 2017)

Seems you have the OPV set at something close normal, that seems a good thing to check.

Some nice photos, i'm not sure the links i provided earlier are crystal clear.

After a bit of digging these are probably better.

https://wiki.wholelattelove.com/images/d/d4/BABIES-CLASSIC_3-Way_Solenoid_Cleaning.pdf

https://wiki.wholelattelove.com/index.php?title=File:HOW-TO-CLEAN-REPLACE-GAGGIA-SOLENOID.pdf&page=11

Not actually sure if they help tho.



Hampus said:


> My best guess is that the piston gets stuck in the top position after the solenoid is engaged during the brew and then remains in this position,


 If it was stuck open, i'm sure you notice it.



Hampus said:


> When running the machine with the blind filter to measure the flow rate, I had some initial success. After switching off the coffee switch, I did finally see a flow of water from the drain pipe and the portafilter was for the first time easy to remove, indicating a successful pressure escape though the solenoid valve!
> 
> The joy was short-lived however when I was unable to reproduce the behavior on later backflushing attempts. Each time after that, the result was the same as before: no water in the drain pipe and the portafilter hard to remove because of the pressure inside.


 I'm not i understand this exactly, i'm guessing after pumping a bit of water through - you retried and got some success. The only thing i can think of why that might be different is the water temp might be lower.

I'm running out of ideas tbh, try the backflushing with water (not any cleaner) with the shower head and disk out (these are nice and clean I guess). It will take a second or two longer.

Try it after steaming when the pressure in the boiler is higher and the water temperature is much hotter, so be careful doing this.


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## Hampus (Sep 20, 2020)

OK, something happened and now the solenoid valve appears to work as it should!

Don't know if it was the last disassembly and cleaning of the valve, the lowering of the brew pressure, or the constant back-flushing I tried for the last few days but now when shutting off the coffee switch I get that delightful flush in the drain pipe again and the portafilter is no longer stuck to the group head.

Thanks a lot for all the help along the way! I'm really glad to have learned a bit more on how this machine actually works and what I should to maintain it.

I still make terrible espresso though, but that's not the Gaggias fault. (My current grinder is no good, waiting on a new Niche Zero to arrive in November...)


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## Blue_Cafe (Jun 22, 2020)

How hard did you hit it? :classic_ninja:


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## Hampus (Sep 20, 2020)

Blue_Cafe said:


> How hard did you hit it? :classic_ninja:


 Yes, I forgot about that!

I actually did try to hit the solenoid a little bit to see if that would get it unstuck  It did nothing, although I did not dare hitting it that hard thinking I'd probably break the electrical coil in the solenoid if I did.


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## Agentb (Feb 11, 2017)

Hampus said:


> OK, something happened and now the solenoid valve appears to work as it should!


 Good news,👍 it doesn't take much gunk or a bit of scale caught somewhere to cause problems. I usually run a little flush after every cup just to push some water through the shower screen.


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