Gaggia 3-way Valve Operation

The Gaggia three way valve is attached to the side of the group head on many coffee machines, and operates to route the hot water through to the coffee puck when pulling a shot.  At all other times, the solenoid valve is de-energised, and routes any remaining pressure above the puck to the drain so that you can safety remove the portafilter after the shot without being sprayed with coffee resulting from the residual pressure.

To check its operation, you should also be able to hear the metal slug inside the solenoid moving as the supply is applied and removed at the start and end of the shot (you may want to disconnect the pump so you can hear the solenoid operating).

If you cannot hear this, then make sure volts are delivered to the solenoid whilst the shot is being drawn.   The voltage will be either 24Vac, 110Vac or 230Vac (230Vac for the Gaggia Classic), so you need to be competent in the use of a multimeter in the presence of mains voltages.   The voltage should disappear as soon as the shot is complete.

If this is correct, remove the solenoid, and blow into the drain port.  Your breath should exhaust through one of the ports (see diagram below).

If it is still not working, then there is most likely some debris in the small internal galleries of the valve, either small pieces of scale, coffee grounds or rubber resulting from the replacement of the portafilter gasket.

The diagram below shows the internal arrangement of the 3-way valve as used on the Gaggia Classic and other models.

If you have a professional machine, the mounting flange may be different, but the operation will be similar.

Here the ports are marked 1 and 2, with port 2 normally closed when the coil is de-energised and the flow being from port 1 to the drain.

The slug inside the valve has a washer on either end, and due to the spring, is normally resting on port 2 completely sealing it. When the supply is connected to the coil this causes the metal slug to move against the spring force, and opens port 2 allowing flow between port 2 and port 1. At the same time, it comes to rest against the third port at the top of the valve (which runs to the drain), sealing that off.

Here is a summary of the test procedures:

1. Are there volts to the solenoid whilst pulling a shot?

2. Can you hear the solenoid slug moving when starting and stopping the shot?

3. If you push an unfolded paper clip into the drain opening, does it get pushed out when the valve is energised?

4. With the solenoid removed, can you blow freely through from the drain to one of the ports?

If the answer to these four questions is yes, then if there is still a fault there must be debris blocking the remaining port (the port from the boiler).  This is the smallest port (only about 1.2mm diameter, so is likely to be the first to be obstructed, generally by scale).  The remaining two ports are about 3mm in diameter, and so are less prone to blockage; any debris on this route are filtered by the shower screen.

If the coil is weak, the washers are worn, or for some other reason the valve is not working correctly, then we have replacement 3-way valves for Gaggia or other makes, in our ebay shop.

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24 Responses to Gaggia 3-way Valve Operation

  1. Mick says:

    Hi, I have posted a couple of other comments but wanted to add here as well as you may be able to help me with another problem.
    After a shot is pulled hot steaming water spits out of the drain pipe and then it continues to drip scalding water in to the drip tray, filling it up very quickly.
    Is this the solenoid or another problem?

    • admin says:

      Hi Mick,

      It sounds very much like the solenoid.

      What causes this fault to correct itself, allowing you to pull another shot successfully (ie it could also be electrical)?


  2. Fidel says:

    I am not getting any water out of my gaggia classic group head, the machine was bought on ebay and it looks as if it has never been used. no scale etc. upon disassemble I took out the solenoid valve and found that one of the holes is not milled out by the manufacturer. I’m not sure if I could mill this out myself with a drill press or If I should just purchase a new solenoid valve or if this is just how it is supposed to look. here is a link with some pictures .;topicseen#new


  3. Fidel says:

    Thanks for the confirmation! I am probably going to have to buy another from a retailer. Too bad they are incredibly expensive though.


  4. Pingback: Gaggia Classic notes | marybicycles

  5. Richard says:

    When I switch it to brew, the voltage drops to about 0.3V and when I stop the shot it goes up to about 4V. Any ideas?

    • Richard says:

      Sorry, those number are with the plugs off the solenoid. I plugged them onto the solenoid and now I get 0V with the switch off and 0.4V with the switch on.

    • admin says:

      The coil is fed with mains, so you would expect to see 230V AC (for a UK version).

      Perhaps you could elaborate on what your issue is and what you are measuring?

      • Steve Morgan says:

        Sorry, I appreciate that this is an old post.

        But my guess is that Richard’s multimeter was switched to DC, not AC, thus recording the average voltage which for a regular mains supply is 0V.

  6. Craig says:

    My Gaggia Classic both brews and produces steam fine although it didn’t really occur to me that I never have dry coffee pucks at the end. However I backflushed for the first time yesterday and nothing came out of the overflow pipe as expected (TBH I can’t remember ever seeing anything coming out of the overflow pipe). I then really, really struggled to get the portafilter off as the pressure build up was so great.

    I removed the solenoid and it all seems clear although I don’t have a voltmeter to test the electrics but from the diagrams in your article I imagine that I wouldn’t be getting anything through the group head/steam outlet if it was shut?
    Any ideas?


    • admin says:

      Please read the article in full as there are test procedures shown.


      • Craig says:

        Hi Steve,
        Thanks for the quick reply.
        If, once I’ve carried out the 4 tests, the solenoid isn’t working, could water still get to the brew head and the steamer without problems (which they are). I thought this might be a test in itself.


        • admin says:

          If the valve is stuck, the solenoid coil is faulty, or there is no power to the solenoid, then then these faults would match the symptoms you have. One of the openings in the valve could also be blocked.

  7. Nigel Young says:

    Gaggia Classic
    Solenoid tests ok for voltage and kicks paper clip when activated but only getting 2oz water through empty portafilter in 40 to 60 seconds.
    Pretty sure no debris in ports as have fully stripped boiler, solenoid and opv, checking all ports clear visual and blow test.
    Could solenoid be weak and not opening valve enough.
    Outer piston doesn’t seem to move only small inner piston?
    Your advice would be much appreciated.

    • admin says:

      If there are *certain* there are no blockages in the solenoid or water paths in the group head, then I would check the pump.

      Operate the pump with the steam wand open to check there is good flow.

      You can also compare this flow to the flow through the group.


  8. David Pearson says:

    Healthy flow from steam wand, but nothing from group head. Have thoroughly descaled from top to bottom, including solenoid. When I switch on – with pump disconnected – what should I hear? There’s a ‘buzz’ but nothing like a piston moving. Could I be looking at a new solenoid?

    • admin says:

      If you disconnect the pump and take the hose off the top of the solenoid you can insert a cocktail stick. That should move up when you power up the machine and turn on the hot water switch.

      If not it could be seized or the coil could be poor. If the coil buzzes, it is probably seized with debris.

      If the solenoid is working, the the passage from the boiler to the portafilter is probably blocked with loosened scale.


  9. David Pearson says:

    Thanks Steve, I’ll try that.

  10. David Pearson says:

    Cocktail stick launched into space, so no problem there and no buzzing this time. But water still dripping only with shower and holding plate removed.

    • admin says:

      In that case you are left with the blockage between the boiler and portafilter, probably the solenoid is blocked with scale I would say.


  11. Gil says:

    Hi Steven,

    I’ve just solved my New Baby Gaggia’s valve problem thanks to your detailed explanations.

    The hardest to do is definitively to unscrew the Solenoid valve. I needed to use a lubricant on the screws.

    So it seems I have a brand new espresso machine thanks to you.

    Have a good day.


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