FairRecycler

@ratty I had exactly the same last year. Pm sent

@phario There isn't a lot of water remaining at all. What I noticed was a 1-2mm long slug. After numerous shots I can't see water accumulation in the PTFE tube neither. M5 16bar plug screw This why the flipping over approach is in place. The PTFE tube won't need to be disconnected to open up the machine, it is designed to reach in the flipped rest position - see attached photo.

Fair point

Yes I thought about that, however I can't understand it. If there is no leak in the tapping system, the level of fluid (level with the tapping point when installed) should be constant @ standard circumstances. It is the best approach as long as water can't get into the cap tube (in my understanding) hence it's commonly used on HX machines where the boiler is only half filled.

I was thinking of a 1/2" copper tube from the top of the manifold to the top of the boiler as a water accumulation chamber with a cap tube on top of it leading to the gauge (which in theory would never get water fed into it due to the increased volume of the tapping system). As water level couldn't reach the top of the chamber (the chamber itself should be sized greater than 90% of the volume of the whole tapping system -BTW I assumed the PTFE tube version would comply with this, obviously I didn't count with the volume of the gauge itself), we could consider the cap tube "dry", so routing, cooling coils, and lower mounting shouldn't be an issue neither. It should also have a good affect on the main flow as a buffer. On the flip side it greatly increases man hours.

I supposed it'll only fill up to 90%, as the air in the tube will be compressed 1:10 @10 bar Very true, but as it fills up completely we can assume it goes through the orifice too and that part of the water won't freedrain for sure, due to the vertical position, and the orifice itself) I don't think so, I'd rather bet on the volume of the gauge inside (from gauge inlet coupler to bourdon) is greater than the 10% of the whole tapping system That's impossible mate At least it is to the best of my knowledge, in the Gaggia Classic, in my top extension mount application.

It seems, I won't get away without making that water accumulation chamber on top of the manifold. At least now I have a tiny bit of room in costs, however I was hoping to make it cheaper than the current version with outsourcing the machining to Eastern Europe. On the other hand it would cover the front panel mount version too, and probably I could get rid of the PTFE tube as well, saving funds sitting on the shelf in the form of a 100m roll. It's a never ending story isn't it?

I`ve been observing the water in the PTFE tube, and I`m not happy. The PTFE tube fills up completely (obviously I didn`t count with the volume of the gauge itself) This could possibly lead to clogs as @L&R questioned, also calcification can build up in the orifice itself, and it also transfers heat to the gauge, possibly causing inaccuracy. I`ve also spotted slugs in the tube after depressurising it, however it doesn`t seem to affect the needle at all (not yet at least, however after repeating the cycles several times the occurences seem identical To say something good too, I`ve found a supplier providing the parts on a reasonable price, however I have to buy 100m of the PTFE tube I need 40cm / unit. LOL

So here is the video what we made with my son (he is 3 yeas old ) this afternoon. Left infeed cap tube, Right outfeed PTFE with  0.5 orifice @ gauge end

That's the gauge end of a 4mm ID dry PTFE tube, so there is nothing but air at that end. At least that's what I'm hoping for.

Good news While I'm waiting for the machined couplers I thought I'll try to make one myself, in order to carry on with testing. After a 2 day torture I managed to get 1 piece done, and Eureka it's holding pressure. My assumption is confirmed now, the 0.5mm orifice in the gauge coupler 100% eliminates the needle flutter, yet it is really responsive to pressure changes, so reflects the actual brew pressure punctually. Later on today I'll film it as well, to let you guys see the result. I'll test it in the next few days and hopefully than I can order the first batch of these couplers. Attached a photo of the latest design, the only difference is the orifice diameter is 0.5mm not 0.2mm.

This is sold by now outside CFUK. It could be moved to SOLD. Thank you

@Blue_Cafe I've just checked what this is Sounds like a good idea to me, however I have no idea if I can find one for this application - an M5 male to M5 female would be just perfect or something with 6mm push for. I doubt any of these existing. I don't understand your concern according to the safety valve I'm afraid. I thought the boiler void acts as a buffer with the current setup anyway. Also there is an orifice in the solenoid valve ( just checked it's 1mm, and I was wrong the in the brew head there is a 2.5mm hole so that won't act as an orifice in my understanding ) to smoothen the flow to the puck. The few commercial machines I've seen has the OPV at the pump outfeed too. May I ask for further explanation please

@phario Thank you for all this, you digged out some very useful information again. Just to clarify, I decided to pull away from adding an extra orifice - the ones in the solenoid valve and the brew head ( both 1-1.5mm diameter by eye) are still in place obviously - simply beacause, my plan is to regulate pressure in the near future with a PWM signal on the pump. This 0.5mm orifice made a significant pressure differential between the pump end and the brew head, leading to a delayed reflection of a pressure decrease at the puck, when the pump is controlled. The main aim of this experiment is to sort the pressure gauge out. I added this extra orifice, as I was interested in the affects. In my opinion the flutter is near enough to the acceptable level, however I'll still try a purpose made snubber at the gauge end. On the other hand I find the article really useful to set the steep beginning of the pressure profile accordingly.

@phario Yes we have very similar thoughts according to the importance of servicability / access. I made a close-up and tried not to shake the camera that much this time I'm not sure I have to go any further to be honest. I'll still try the coupler with 0.5mm orifice. PTFE tube without orifice I don't think I'll offer the PTFE tubed version to front panel mount, due to food hygiene concerns @Blue_Cafe mentioned. I never thought drilling tiny holes could be this challenging. I'm getting closer day by day