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Gaggia Classic, problem with backflushing


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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:

  1. 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.
  2. 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.
  3. 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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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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33 minutes ago, 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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Current: Lelit Elizabeth / Niche Zero / VST baskets / Distilled water + 100mg NaCO3/L

Previous: Gaggia Classic | Eureka Mignon | Rocket Cellini Evo | Profitec 700 | Profitec T-64 | Gene Cafe CBR-101 | Kinu M68 | Feldgrind 2 | La Pavoni Europiccola 2012

Also at: CoffeeTime Forum & Niche Zero Owners Group

 

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9 hours ago, 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.

 

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:

  1. 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.
  2. 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.
  3. 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?

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.

Current: Lelit Elizabeth / Niche Zero / VST baskets / Distilled water + 100mg NaCO3/L

Previous: Gaggia Classic | Eureka Mignon | Rocket Cellini Evo | Profitec 700 | Profitec T-64 | Gene Cafe CBR-101 | Kinu M68 | Feldgrind 2 | La Pavoni Europiccola 2012

Also at: CoffeeTime Forum & Niche Zero Owners Group

 

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31 minutes ago, 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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1 minute ago, 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?

Current: Lelit Elizabeth / Niche Zero / VST baskets / Distilled water + 100mg NaCO3/L

Previous: Gaggia Classic | Eureka Mignon | Rocket Cellini Evo | Profitec 700 | Profitec T-64 | Gene Cafe CBR-101 | Kinu M68 | Feldgrind 2 | La Pavoni Europiccola 2012

Also at: CoffeeTime Forum & Niche Zero Owners Group

 

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16 minutes ago, 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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12 hours ago, 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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20 minutes ago, 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!

Current: Lelit Elizabeth / Niche Zero / VST baskets / Distilled water + 100mg NaCO3/L

Previous: Gaggia Classic | Eureka Mignon | Rocket Cellini Evo | Profitec 700 | Profitec T-64 | Gene Cafe CBR-101 | Kinu M68 | Feldgrind 2 | La Pavoni Europiccola 2012

Also at: CoffeeTime Forum & Niche Zero Owners Group

 

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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".

Edited by MrSmartepants
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