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Gaggia Classic, problem with backflushing


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35 minutes ago, 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:

Quote

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

Quote

Avoid contact with humidity, strong acids, thin aluminium.

 

I would just stick with the Gaggia stuff tbh

Edited by Blue_Cafe
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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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11 hours ago, 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…)

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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22 hours ago, 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

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! 👍

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

IMG_0359.thumb.jpeg.96f42da4fe2da5634f99d8317c797791.jpeg

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.

IMG_0364.thumb.jpeg.59c47d52c5e4260584d7e4318db9f8dc.jpeg

Top part seen from below, no blockage here!

IMG_0368.thumb.jpeg.69ce3e5d50d815d280d2fae57927c5ba.jpeg

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.

IMG_0369.thumb.jpeg.26808561bec895a182184f22ee45fc97.jpeg

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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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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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.

14 hours ago, 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. 

15 hours ago, 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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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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37 minutes ago, 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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7 hours ago, 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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