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Rancilio S26 running off tank letting hot water back through inlet hose

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  • Rancilio S26 running off tank letting hot water back through inlet hose

    Hi CSers

    I've upgraded from my Silvia with a used Rancilio S26 from another CS member and trying to set it up this weekend.

    I'm having a bit of trouble reliably drawing water into the the machine & wondering if anyone has suggestions on what's going on.

    At the moment, I've set up an external water tank to feed the S26. I don't want to drill through the counter top just yet to plumb into mains and have read that running from a tank is commonly done successfully. There's a pressure adjustment screw on the rotary pump to increase pressure accordingly if not running on mains pressure.

    The machine pulls water from the tank easily when first switch on, but once the machine gets hot it won't reliably pull fresh water and instead will sometimes let boiling water/steam comes back through the inlet hose (hose gets too hot to touch). I've elevated the tank temporary but without seeing an improvement. It doesn't seem to be running the pump backwards but hot water and bubbles of air are moving through the hose and giving gurgling sounds at the tank. You can hear it at the end of this short video:

    In this second video, you can see the machine pull water fine at the beginning, then stop and be unable to draw any more water (to refill the boiler):

    I'll try to rig up a temporary mains connection but knowing others have run from tanks makes me think the issue is elsewhere. Is the pump misbehaving, a valve not closing or something else?

  • #2
    Wow! Nice to see a video! Are you using distilled water? Is your water level probe clean? The pump on and off can indicate a faulty signal from the probe.


    • #3
      Also, you have an issue with your OPV or/check valve downstream from pump. I'll look at the schematics for the S26


      • #4
        Try to take an image of the interior for us - especially the pump and hydraulic routing to the OPV. Your level controller may be an issue - or the wiring to and from it. Check your wiring visually if you feel competent enough (machine off, desteamed and unplugged from owner point).


        • #5
          Rancilio S26 running off tank letting hot water back through inlet hose

          The check valve and OPV should look like this.
          Attached Files


          • #6
            R.33 through R.36 is definitely a culprit and so is R.81 through F.70 (check valve from pump).


            • #7
              If none of this works, take it to a technician. Better than getting super frustrated.


              • #8
                Thanks so much sprezzatura!

                I will take photos and report back. The machine is very easy to pull panels and get interior access to.

                I'm happy checking wiring and probing with a multimeter. But yes if I can't diagnose I'll take it to a coffee tech.


                • #9
                  I'm using bog standard Sydney tap water, less than 10L has gone through the machine though.

                  I will have to check the water level probe, after I look up the exploded diagram to find it


                  • #10
                    It'll be on top of the boiler, dude. A female spade connector will plug into it and the wire will go to the black box that is the level controller.


                    • #11
                      Standard water won't cause conductivity issues with the controller/probe.


                      • #12
                        ... standard Sydney bog water [emoji14]


                        • #13
                          Click image for larger version

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                          Level probe is in the middle white connection with white or grey wire.


                          • #14
                            Hello voicecoils,
                            Interesting challenge you have there however,you say your getting a reverse flow into the water tank and making the hose too hot !!That is not possible if you have correctly installed your inline one way valve (non return valve).
                            I have two commercial espresso machines set up presently,both with Non return valves between the water tank and the rotary pump,one a fancy brass one and the other a cheap $10 unit from bu___'s.
                            Both work perfectly well,I also have two other commercial single group's as my work identically set up,also with non return valves (essential when using rotary pumps).
                            In your videos I was unable to see any,do you have them fitted?


                            • #15
                              I haven't fitted an external nonreturn valve, I thought the machine would have something internal, but may well be mistaken! Thanks for raising that point.

                              The line is definitely getting hot from boiler water. It stays perfectly cool up until the point where the pump starts making funny struggling noises then the hose heats rapidly with spitting gurgling steam sounds.