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Non Return Valve

Hey All,

I have an L1 that has the addition of the "non return valve". If memory serves, this was an addition to help stop the problem that a few reported around a thermal stall of some sort. Anyway, for the first month or so, I had/saw no issues. Now, every time I pull a shot, I get a significant amount of water draining from the drain hole located on the front of the machine. Any thoughts of why this is happening? I am having no other issues with my machine. I believe that this non return valve was not included after a very short time so many may not have it.

Thanks. Cheers.



  • Hi Danny

    That is the expansion valve opening

    This should only really occur on warm-up, if it is happening when you pull a shot the expansion valve needs adjusting

    If you go to the NRV/expansion valve you will see a white nylon adjustment screw

    Turn this screw 3 turns in a clockwise direction and that should resolve the issue

    Kind regards

  • Thanks Reiss. When I am back in town next week, I'll give it a try and report back to the forum.
  • So the problem just kind of went away so no changes made...

    Reiss, can you help my understanding of this valve? Is it simply there as an air vent to release air if it ever enters the system? I love knowing how stuff works but I am not clear on the mechanism here.


  • hi danny

    your machine has a non return valve with an expansion valve

    when the machine is cold and is turned on, the system obviously warms up

    as the system warms you get hydraulic pressure created in front of the non return valve, as the non return valve is preventing the water in front of the valve from expanding back into the boiler

    the expansion valve opens when this situation occurs to allow the excess pressure to be relieved

    kind regards

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