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I previously worked on Virtual Reality and other hardware at Valve.  I currently work at Google[x].

Prior to starting at Valve, I built computer peripherals such as keyboards, mice, and joysticks that were designed to be used inside MRI machines.  My company, Mag Design and Engineering, sold these devices directly to researchers at academic institutions who used them to publish scientific papers in peer-reviewed journals.

After work, I spend time on many different types of projects that usually involve circuit design, machining, material selection, and general fabrication/hacking.  My favorite place to be is my home workshop.

ben dot krasnow at gmail

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Sunday, November 21, 2010

Adding a pressure gauge to a Delonghi espresso machine

I bought a new espresso machine with the main intention to hack it and modify various parts while enjoying really good coffee along the way. This machine is a DeLonghi EC155 and cost $90 at Fry's Electronics with $20 mail-in-rebate. I normally don't buy anything that includes a rebate, but I made an exception in this case since $90 is already a good price for this machine.

The EC155 has a stainless steel boiler, "15-bar" pump, large water reservoir, separate baskets for single and double shots, and a pressurized portafilter. Espresso purists will tell you that a pressurized portafilter is just a kludge that is meant to help newbies get the right extraction time despite improper grind size or tamping, but I might disagree -- more on that later. In any case, this machine is a really great value, and a HUGE upgrade from steam-powered machines.

I previously hacked a steam-powered machine and added an air pump and temperature regulator to have more control over the brew process: http://benkrasnow.blogspot.com/2009/12/using-my-hacked-espresso-machine.html. The machine worked pretty well, but it was time to retire it because of a few nagging problems including a leaky portafilter, overall junky basket design, and other very difficult-to-fix items.


The DeLonghi EC155 with added pressure gauge.

I could not believe the unit would ever reach its stated "15-bar" pressure, and I was also curious what the brew pressure really was for an average shot. I started by removing all of the machine's guts from the case. It's built surprisingly well. The grouphead is made of very thick cast metal (probably an aluminum alloy), and the boiler is all-stainless with brass fittings and silicone seals.The pump is a ULKA brand pump. There is no obvious model number, though.

The boiler contains a large heating element and two separate thermal switches -- one for espresso, the other for steam generation. The boiler empties into the grouphead via the brass tube sticking up through the boiler's bottom. This way, the water level must rise above the brass tube's top for water to enter the grouphead. When the machine is off, there is no chance of water leaking out.

The brass tube also contains a spring-loaded valve that keeps the grouphead closed until the pressure in the boiler reaches 75 psi (5 bar). I suspect this is to prevent the grouphead from leaking while using the steam wand.


I removed the original 4mm plastic tube that ran from the pressure regulator to the boiler and replaced it with 1/8" PFA tubing. I added a tee in the line and attached the pressure gauge with more pipe fittings and 1/8" compression adapter. The machine will reach 13 bar when the portafilter is completely blocked (no flow), but is usually 7-8 bar during a double shot. Thus, the pressure regulator doesn't do anything in normal operation since the pump cannot maintain more than 8 bar during an average brew flow rate. I may be hacking this part in the future to have more control over brew pressure. However, I think the espresso experts agree that the brew process should have constant flow, not constant pressure.

The machine is designed to use a pressurized portafilter, and produces LOTS of crema with the pressure valve in place. I removed the valve and tried a few shots, but they did not taste as good or have enough crema, and it was very difficult to make the shot last more than 15 seconds. I used the finest grind that I could muster and tamped very hard, but the shot was still underextracted. I suspect that the machine's designers didn't worry about the portafilter geometry, or depth of the coffee puck since they knew the valve would regulate the brew pressure and extraction time. It may also be true that the machine's pump flow rate is not high enough to produce enough pressure without the portafilter valve. I did some tests:

10.4 seconds per ounce at 7.5 bar (170 ml/min)

9.1 seconds per ounce at 5 bar (192 ml/min)

3.3 seconds per ounce at 0 bar (530 ml/min)

I am guessing that the pump is specifically sized so that the brew pressure will be about 7.5 bar and a double shot will take exactly 25 seconds.

57 comments:

  1. I have the same machine and was thinking about modding it. I was looking at being able to adjust the temperature by adding a PID temperature control but I was wondering about pressure as well. I've heard 9 bar is about the ideal pressure you want so maybe there would be a way to coax higher pressure out of the pump.

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  2. Samantha, the maximum brew pressure is set by a relief valve that is mounted in-line between the pump and the boiler. However, for normal brewing it seems the pump cannot raise the pressure high enough to activate the relief valve while still maintaining a normal flow rate. I think you could slow down the flow rate so that a double shot takes 30 or 40 seconds, and brew at a higher pressure, but this may not make better-tasting coffee. Or maybe it would -- give it a try!

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  3. Actually I'm getting a 120V to 240V transformer and a dimmer switch so I can give the pump a little more voltage, maybe 140V max? Anyway, it'll give me something to play around with. I'm also ordering the Le'lit PL53 grinder, which has crazy adjustably and we will see where I get with just that. I've read people with much more expensive espresso machines they dial it down because where it's set out of the box is way too fine so nothing ends up coming out. I still need to do more research and see what other people have done regarding adjusting pump power.

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  4. Wow, that's some serious hacking! Good luck! Let everyone know how it turns out.

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  5. lack of crema and taste when using unpressurised baskets most probably means stale beans.
    if beans are fresh, then it should be ground finer and tamped harder with a proper tamper.
    you might wanna change your grinder to one which provides a more consistent particle size too.

    I had 3 thermoblock machines which served me very well, along with 2 levers and a heat exchanger machine. for me, fresh beans makes all the difference, followed by a decent grinder. machines takes the backseat.

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  6. James, it's good to hear from an espresso fan who doesn't put too much emphasis on the machine. As you've probably seen, a lot of folks on espresso forums seem to think that there is some sort of magic instilled in certain espresso machines -- especially those made/designed in Italy.

    When I make drip coffee, I much prefer lighter roasts, and so I typically have "medium roast" beans in my kitchen, and use those for espresso too. I know this isn't usually recommended, but may explain why results are a little different from the norm.

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  7. Tell me about it. I've heard of this guy who uses cheap lavazza pre-packed beans with his 6000usd espresso machine. lmao.

    Yes lighter roasts tend to give slightly lesser crema, esp those roasted to just above 1st crack.
    Drip coffees are wonderfully flavourful. very enjoyable but not as much craft work as espresso. I guess that's why i seem to enjoy making espresso more cuz it's a very technical hands-on process

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  8. How did you remove the 4mm tubing, and reinstall the 1/8"? I have not seen these fittings before now. Where can one buy these?

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  9. Anonymous, I ended up completely removing the existing brass fitting, and replacing it with a brass bulkhead fitting that had a 1/8" pipe thread. I then used 1/8" compression fittings with the PFA tubing. This worked OK, but there are probably better methods. Using larger tubing with an internal brass insert in the compression fitting would be an improvement

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  10. Ben, the grinder is as important as the machine and the beans. You can get good pulls from the $200-$500 machines with a good grinder(used commercial grade are affordable) and fresh beans(<2 week old). You'll get great pulls with a good grinder AND a machine PID'ed(~200DegF) and puck pressure adjusted to ~9 bars.
    your grinder must be capable of consistent particle size and fine enough to stop up the flow with a 30 lb tamp.

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  11. Great work, Ben. Here's a very lame question: How'd you get into the guts of the thing? I've taken out the four black Philips screws but that didn't free the upper part. Do the knobs need to be levered off? Does the top need a bit of persuasion? The hinged cover? Thanks in advance for any tips

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  12. GreenMter, the steam control knob will probably need to be removed. I think it is just a friction-fit, so it simply pulls off. After removing the bottom panel, there are other screws that affix the top located inside the machine. You'll need a long screwdriver or allen key. I seem to remember this device using torx or security screws somewhere on it as well. Let me know how it goes.

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  13. Hi Ben. I stumbled across your blog looking for a way to add a PID to my EC155. Your comment about needing the pressurized portafilter basket is probably half true. After removing the pressure release valve from my double shot basket it took about a month for me to get really consistent puls that take longer than 20 seconds. After getting the grind correct, and using fresh roasts, I get much better results. It is much easier now to underextract, but with enough practice and attention to tamping this is not much of a concern at all. I just wish the portafilter was slightly larger...

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  14. Hi Ben. I bought this machine yesterday but I didn't notice that it needs 120 volts. And I have 220 volts only.
    Is it possible to replace something in the machine to fix this? Or does power go to the pump directly?
    Thanks

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  15. Xander1563, the heating elements and pump are 120V. Your best bet is to use a very large 220/120 step-down transformer, or get a different machine.

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  16. Thank you very much for your response! I was going to go to Delonghi service, but now that I know it's useless I save that money to buy another EC155 machine. Transformers are pretty expensive where I live

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  17. Hi Ben,
    Very nice work on this post!!

    I have a little problem in my delonghi EC200, after 4 months using it to produce my espresso the machine started to get one problem.
    When I try to make a shot the coffee don't come out, or it get out but without crema and really slowly, one drop after another.
    I don't know if is the pressure or the portafilter.
    I tried without coffee on the filter, and the water come out "normally".
    Do you have some advice's for me?

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  18. Andre, the machine's pump may not be supplying enough flow at brew pressure. Perhaps the pump has broken. Replacing it would be possible if you could find another similar espresso pump. Try searching around for replacement espresso machine pumps.

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  19. I did a lot of experimenting as well. I learned that with these machines that use a spring loaded valve at the brew head (instead of the more expensive solenoid valve), the actual pressure at the coffee puck is much lower than the pressure you are reading with your gauge. If you were to put a second gauge mounted on your portafilter as a test - you would see that the 4-5 psi required to open your spring valve is about how much less brew pressure you have. With your gauge mounted before the boiler, your coffee puck will always be seeing about 4-5 bars less than what your gauge reads.

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  20. Hi Ben,

    Can you please help me, I am trying to dismantle the unit and I think I need to remove the steam control valve. However I am worried about breaking it! any tips or method for how you did it?

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  21. Scott, I think the knob just pulls straight off. Use two screwdrivers as levers under opposing edges of the knob.

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  22. worked like a charm thanks so much, especially for the prompt reply!

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  23. Hi. Your post about DeLonghi EC 155 with detailed photos was BINGO for me J I was looking for this information for a week and your post helped me very much. Pressure after valve but before boiler on my DeLonghi EC 155 is good. But from holder group to cup… water stopped punching portafilter , even without coffee. I weakened valve from holder group. Now some questions:

    1) You say: I removed the original 4mm plastic tube that ran from the pressure regulator to the boiler and replaced it with 1/8" PFA tubing……… For what? Larger diameter of pipe makes the greater water flow , which goes from pump to boiler?

    2) Can you exactly explain way of new connection? Boiler – Tee - Pressure Valve ….. and on the other connection on tee you have pressure gauge ? is it like this?



    Thanks a lot for help .

    Best regards,

    Aleksandre

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  24. Very cool! I found this linked from the coffeegeek.com forums.

    How did you make the connection to the pump? It looks like you have an additional adapter there? And were do you get all the parts? McMaster-Carr or something?

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  25. Ben, yes all parts are from McMaster. I used a male pipe fitting with an 1/8" compression output on the pump.

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  26. I have some problems with my delonghi ec155
    Did u have an original diagram of this machine?

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  27. I am KumarKS. I got impressed by one of your video about " Choosing a transistor " in youtube. Later became your fan. Now I see your picture everywhere - blogs, expo, even in Make magazine. You doing a great job.

    I found a common problem with this Delonghi EC155 coffee machine. After I am using for few months, the machine is not working. While troubeshooting, I found the switch at the front is not making proper contact. So I opened the switch and found surprising. Even though the machine is rated as 1100W. The switch contact is not even affordable for 5A at 220V. Now I am modifying with normal on/off switch externally.
    I need your help here. I want to know what is condition of the PUMP / Heater....at each position of the switch - is it ON or OFF?. I found two thermal switches in series with the heater. At certain position of the front panel switch they bypass one thermal switch. I am not sure about this position. If you can guide me on this. I will find it much helpful. Thank you very much.

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  28. The two thermal switches are used to set the boiler temperature for espresso (below the boiling point) and steam wand (above the boiling point). Turning the switch should change which sensor is being used. The most-clockwise position turns on the pump. Good luck!

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  29. Thank you so much for your kind and prompt reply. I will follow as per your instructions - KumarKS

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  30. This comment has been removed by the author.

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  31. Dear Ben, Thank you so much for your guide lines. With only two external ON/OFF switch, I was able to make it working. One switch for the Pump and the other switch to bypass one of the thermal Switch. It's working fine. Thank you again - KumarKS

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  32. if the pump is a ulka ep5 (i have check it), just like silvia, why does the pressure is not the same? Is it the Water Valve next to the pump that reduce de pressure?

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  33. Ben, Recently when I went to use my EC155, it would draw shots of espresso, but would be cold. The top of the machine usually gets pretty warm, but stayed cold.
    Can you give me suggestions to check/replace or should I just purchase another machine?

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  34. drew2u, it sounds like the problem is with the thermostat or the heater element itself. Getting replacement parts might be pretty difficult, but it should be easy to determine which part is bad by measuring their resistances.

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    Replies
    1. Ben, Thank for a real fast reply. I probably won't get anything from Delonghi for a week. I did see that some parts are available and I'll let ya know what I find out. Thanks again!

      Delete
  35. Anonymous, there is a pressure relief valve that sets the maximum system pressure.

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  36. Ben, the pressure relief valve that you mention is the white plastic device connect to the pump, that we see in the 3.º image in this page?
    If so, do you think it is possible to change the OPV to increase the pressure or to increase the pressure allowed by this opv?

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  37. Hi Ben
    I was looking information about disassembling a Delonghi EC155 and came across your blog. Unfortunately, I am not sure how to reconnect the pump because I bought a used machine and I am not sure if all the pieces and connections are actually inside the machine or if there are some missing parts. I just need to see the connections of the pump. Do you remember how the pump is connected? Is it possible that you send me a picture? I’d really appreciate it!

    Regards

    Julio

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  38. Hi Ben
    Do you know how it can be put an PID controller in EC 155 to increase the temperature? I noticed the 2 thermostats inside the machine, but I don't know which is for coffee and which for steam and how to bypass the coffee thermostat and connect the PID, SSR and K sensor. I would like to install an PID because I think the temperature of the coffee should be a little higher.
    Regards,
    Tib

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  39. Anonymous, try disconnecting one of the stock temperature switches in the machine, then turn it on, and see if the boiler is getting hot. If not, you've found the correct switch. Put your SSR in place of the stock temperature switch then attached the temperature probe to the boiler.

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  40. Hello Ben,
    I have a big problem with my deloghi ec155.
    When I try to make a shot the coffee don't come out, or it get out but without crema and really slowly, one drop after another.
    I takes 18 min. until i get a cup of cofee.
    I'm sure it have to do with pressure.
    I tried without coffee on the filter, and the water come out "normally".
    Do you have some advice's for me?
    The machine is brand new, only 3 day;s old, but from the beginning, it don't works how it have to be.
    This is my 8 delonghi espresso machine in mora as 20 years, and never i got a problem with.
    I wrote to delonghi a email for what i can do, the answer was, i have to go to Brasil, live self in the Dominican Republic, so that's no option to do.
    Please help me, what i can do.
    Regards
    Marianne

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  41. Marianne, it sounds like the pump is defective. If you can't exchange the machine for a new one, then you'll have to buy a replacement pump. I doubt repairing it would be possible without access to a well-equipped machine shop.

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  42. Hi there I wonder what is the white substance (paste) between the thermostat and the boiling tank?

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  43. Anonymous, it is grease meant to improve thermal conductivity between the two metal surfaces: http://en.wikipedia.org/wiki/Thermal_grease

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  44. Hi Ben, Great post but I don't think i got the tools, or the expertise to test this out. Could the pump loose power overtime? I'm noticing less pressure on my machine. I haven't changed my beans or the level I grind them. But not getting a crema anymore and taking longer for espresso to dispense. I've had the machine for about 6-7 years. I'll try cleaning the system and see how it goes.
    thanks in advance.
    Farzam.

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  45. I had the same problem with espresso coming out way too slowly. I followed a tip I'd read about...disassemble the filter as you would for cleaning. Take the actual filter disk and try looking thru it. If blocked at all, use tongs and hold it over a flame, both sides, while gently tapping it against something solid. It will burn off and remove the gunk that is causing the clog. Make sure the flat plastic disk is off before attempting to look thru or do any burning...

    Now for my question...machine is making coffee but it is cold and also seems to be leaking from underneath. Has it died or is it fixable??? Thanks!

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  46. Update to above...doesn't appear to be leaking now. Unplugged and restarted and it made a hot espresso. Half hour later tried again and it was cold, and no steam from wand either...a short in the wiring?

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  47. cursichella, if everything seems to work, but the machine will not produce hot water or steam, it sounds like the heating element is broken. If at least steam or hot water is produced, the problem may be a thermostat (the machine has a separate thermostat for steam and hot water).

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  48. Hi Ben, I bought the same machine and took it apart last night. I just found your blog after the fact and am happy I did. Out of the box my machine didn't have enough pressure to push through a single in 40+ seconds. I suspected a vib pump problem. I dismantled the pump and it looked ok, then the pressure regulator. I know this is asking a lot but do you remember the orientation of the little pink part in the regulator? I have mocked up a image of the valve, I believe my pressure relief 2 valve was letting far too much liquid/pressure out because it doesn't seat well (it seats on a plastic rib). Also, i don't understand the need for pressure relief 2 as PR1 should work just fine.

    http://i103.photobucket.com/albums/m132/r32sweet/f0572e23-fb36-4d58-ae91-9079f631d26f.jpg

    I'm thinking of blocking PR2. What do you think, and thanks for posting your work!

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  49. Alyre, I'm afraid that I don't remember that level of detail. If you have a pressure gauge, you could connect it directly to the pump to determine if the pump or the regulator is the problem. My guess is that the pump with its moving parts is the more likely failure. Good luck!

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  50. Thanks Ben,
    I have an update. I was really convinced the pressure regulator was dumping too much to the tank so I plugged PR2. I then ran the machine and no luck. Then I installed a pressure gauge after the regulator before the head. The pressure maxed the gauge at 7 bar so the pump and regulator are fine. I then installed the gauge under the head and found the pressure maxed the gauge again. An important thing to note is the pressure valve in the head. Water must build in pressure before the head will eject it to the grinds. This makes timing a shot impossible as the pump needs variable time to build pressure before water is released to the grinds. This means volume might be the regulation in knowing when the shot is done. After verifying pressure I pulled a shot and nothing. no drips even. I then backed off on my grind fineness and am now able to pull half way decent shots. I believe the basket holes are way too small and clog rapidly. I'm now going to pursue a proper basket. I've long removed the pressure regulator in this basket btw.
    Takeaways:
    -The basket is too fine
    -Cant time shots
    Future mods:
    -change the way cold water enters the head (redirect it to the bottom of the boiler so cold water isn't mixing well with the hot before out to grinds)
    -because of above and for greater temp control add a PID
    -Figure out what to do with the portafilter, retrofit a different one or at least get a proper basket

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  51. I am having a problem similar to cursichella's. We've been using ours successfully for about 6 months, but recently the burner won't heat for espresso. If I turn the knob to the steam setting, I can get the burner to heat up enough for a few shots, but it doesn't seem to maintain the temp. If I don't heat it up with the steam setting, the coffee is cold. I'm thinking an issue with the thermostat or thermal switch may be responsible? Any suggestions for troubleshooting?

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  52. Perhaps your brew temp switch (100C) has faulted open? it's normally closed until reaching aprox 100C, at which point it opens which stops current through the heating element. The steam setting uses the same type of temp switch although is set for 110C. If you unplug the wires to the thermal switch and check with a multi meter it should be closed. Thermal switches are pretty cheap if you need to replace one. My high temp is the one with a red marker dot on it and was also closest to the back.

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  53. hi there pressure guage alwsoume guages are alwsoume

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  54. Hi Ben,

    I have the similar "low pressure" problem with my EC 155. I've replaced the pump but the problem still exists :(

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  55. hi ben, it seems that relaxing the tension of the spring loaded mushroom shaped valve in the brew head, you can increase the pressure, up to the desired 9 bars:
    http://www.youtube.com/watch?v=yrB2Dr-6q9s

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